Now Archived and Forked

PMHTTP will not be maintained in this repository going forward. Please use, create issues on, and make PRs to the fork of PHMTTP located here.


Carthage compatible

PMHTTP is an HTTP framework built around URLSession and designed for Swift while retaining Obj-C compatibility.

We think URLSession is great. But it was designed for Obj-C and it doesn't handle anything beyond the networking
aspect of a request. This means no handling of JSON, and it doesn't even provide multipart/form-data uploads. PMHTTP
leaves the networking to URLSession and provides everything else. Features include:

  • Requests can define parse handlers that execute asynchronously separately from the completion block, and
    requests can be canceled while parsing and the completion block sees the correct result.
  • First-class JSON support using PMJSON.
  • Structured results and high-quality errors; no more treating URLError.cancelled as a network error.
  • Strongly-typed results.
  • Thread safety.
  • Intelligent cache handling.
  • Requests can be defined once (including a parse handler) and executed many times, just like URLRequest.
  • Configurable automatic retrying of failed requests when safe.
  • A configurable base URL, allowing for switching between staging and production with no change to the code
    constructing the requests.
  • Support for Basic authentication.
  • multipart/form-data, application/x-www-form-urlencoded, and JSON upload support.
  • Built-in request mocking support without using method swizzling.
  • Nothing uses the main thread, not even completion blocks, unless you explicitly ask it to.

PMHTTP was designed specifically for the HTTP functionality that Postmates needs. This means
first-class REST support with a focus on JSON. But there's some functionality it doesn't handle
which we may get around to doing at some point (see issues). Pull requests are welcome.

Table of Contents


A typical GET request looks like:

let task = HTTP.request(GET: "search", parameters: ["query": "cute cats"])
    .parseAsJSON(using: { (response, json) in
        return try, Cat.init(json:))
    .performRequest(withCompletionQueue: .main) { task, result in
        switch result {
        case let .success(response, cats):
            // Do something with the Cats.
        case let .error(response, error):
            // Handle the error. This includes network errors, JSON parse errors,
            // and any error thrown by Cat.init(json:).
        case .canceled:
            // The task was canceled. Ignore or handle as appropriate.
// task can be canceled and can be queried for its state
// and this can be done from any thread.

A POST request might look like:

let task = HTTP.request(POST: "submit_cat", parameters: ["name": "Fluffles", "color": "tabby"])
    .parseAsJSON(using: { result in
        // POST parse blocks take a single `result` argument because 204 No Content is a valid
        // response. The `result` enum vends an optional `value` property, and has a
        // `getValue()` method that throws an error if the response was 204 No Content.
        return try SubmitCatResponse(json: result.getValue())
    .performRequest(withCompletionQueue: .main) { task, result in
        switch result {
        case let .success(response, value):
            // value is a SubmitCatResponse.
        case let .error(response, error):
            // Handle the error. This could be a network error, a JSON parse error, or
            // any error thrown by SubmitCatResponse.init(json:).
        case .canceled:
            // The task was canceled.

A multipart/form-data upload might look like:

// with photo
let req = HTTP.request(POST: "submit_cat", parameters: ["name": "Fluffles", "color": "tabby"])!
// We could add the image synchronously, but it's better to be asynchronous.
// Note: There is a convenience function to do this already, this is just an example.
req.addMultipartBody { upload in
    // This block executes on a background queue.
    if let data = UIImageJPEGRepresentation(catPhoto, 0.9) {
        upload.addMultipart(data: data, withName: "photo", mimeType: "image/jpeg")
let task = req.parseAsJSON(using: { try SubmitCatResponse(json: $0.getValue()) })
    .performRequest(withCompletionQueue: .main) { task, result in
        // ...


You can modify the properties of the global HTTPManager object at any time, but to make setup
easier, if your UIApplicationDelegate or NSApplicationDelegate object conforms to the
HTTPManagerConfigurable protocol it will be asked to configure the HTTPManager the first time
the HTTP global variable is accessed. This might look like:

extension AppDelegate: HTTPManagerConfigurable {
    public func configure(httpManager: HTTPManager) {
        httpManager.environment = HTTPManager.Environment(string: /* ... */)
        let config = URLSessionConfiguration.default
        config.timeoutIntervalForRequest = 10
        // PMHTTP defines a default User-Agent but we can supply our own
        config.HTTPAdditionalHeaders = ["User-Agent": myUserAgent]
        httpManager.sessionConfiguration = config
        if let (username, apiKey) = getAPICredentials() {
            httpManager.defaultCredential = URLCredential(user: username, password: apiKey, persistence: .forSession)
        httpManager.defaultRetryBehavior = HTTPManagerRetryBehavior.retryNetworkFailureOrServiceUnavailable(withStrategy: .retryTwiceWithDefaultDelay)

Detailed Design

PMHTTP was designed with 6 goals in mind:

  • Be as Swift-like as possible while retaining Obj-C compatibility.
  • Speed, with an emphasis on being concurrent by default.
  • Thread safety wherever it makes sense.
  • Explicitness and type safety. For example, PMHTTP doesn't auto-detect the return type but requires
    you to declare what response format you're expecting.
  • Correctness, which includes avoiding surprising behavior.
  • Make it easy to add new functionality, such as auto-retrying and network mocking.


The overall manager class for PMHTTP is HTTPManager. This is the class that allows you to
configure various global properties and to create new requests. Multiple managers can be created if
desired, but a single global instance is provided under the global property HTTP (for Obj-C this
is [HTTPManager defaultManager]). All properties and methods on this class are completely

Configuration of the shared HTTP instance can be done by adopting the HTTPManagerConfigurable
protocol on your app delegate. This protocol provides a method that can be used to configure the
shared HTTPManager object the first time the HTTP property is accessed. This design allows you
to ensure the shared instance is properly configured prior to first use even if it's used prior to
the normal entry point for your application (e.g. inside some class's +load method). Do note,
however, that this method will be executed on whatever thread is first accessing the HTTP
property, and so it should be safe to run from any thread.

Important: The shared HTTP instance is a convenience intended for use by the application. If
you're writing a shared component (e.g. a framework) that uses PMHTTP, you need to carefully
consider whether using HTTP is appropriate or whether you should be using a separate instance of
HTTPManager. The use of HTTP is only appropriate if you want to automatically adopt any
configuration the application provides (including environment and default credential).


HTTPManager has a property environment of type HTTPManager.Environment. An environment is a
simple wrapper around a URL and represents the base URL that requests should use if the request
is not made with an absolute URL. You may wish to create your own extension that looks something

extension HTTPManager.Environment {
    // @nonobjc works around "a declaration cannot be both 'final' and 'dynamic'" error.
    @nonobjc static let Production = HTTPManager.Environment(baseURL: productionURL)
    @nonobjc static let Staging = HTTPManager.Environment(baseURL: stagingURL)

The environment is also used to determine whether a given request should adopt the default
credential configured on the HTTPManager. Only requests for URLs that are prefixed by the
environment will use the default credential. Requests for any other URL will have no credential by
default, though a credential can always be added to any request.


Requests in PMHTTP are objects. In a pure-Swift world they'd be structs/protocols, but they're
objects in order to be compatible with Obj-C. Unlike URLRequest, PMHTTP requests are inherently
mutable (so they're like NSMutableURLRequest). They're also the only public component of PMHTTP
that is not thread-safe, though it is safe to access a request concurrently as long as no thread is
mutating the request (which is to say, reading values from the request does not perform any internal

Requests are split into a hierarchy of classes:

  • HTTPManagerRequest - The root request type, which contains parameters and methods that are
    applicable to all requests.
    • HTTPManagerNetworkRequest - The parent class for all requests that do not have a parse
      • HTTPManagerDataRequest - The class for GET requests that do not have a parse handler.
      • HTTPManagerActionRequest - The class or parent class for POST/PUT/PATCH/DELETE requests that
        do not have a parse handler.
        • HTTPManagerUploadFormRequest - The class for POST/PUT/PATCH requests without a parse
          handler that have a body of either application/x-www-form-urlencoded or
        • HTTPManagerUploadDataRequest - The class for POST/PUT/PATCH requests without a parse
          handler that have a body consisting of an arbitrary NSData.
        • HTTPManagerUploadJSONRequest - The class for POST/PUT/PATCH requests without a parse
          handler that have a body consisting of a JSON value.
    • HTTPManagerParseRequest<T> - The class for any request that has a parse handler.
    • HTTPManagerObjectParseRequest - The class for requests made from Obj-C that have a parse
      handler. Similar to HTTPManagerParseRequest<T> but the parse result is always an AnyObject?.

This hierarchy means that every class can provide only the methods/properties that make sense for
all requests of that class type. For example, only HTTPManagerUploadFormRequest requests allow for
adding multipart bodies.

Requests include properties for configuring virtually every aspect of the network request. A few
properties inherit default values from the HTTPManager object, though these default values can
always be overridden. One property of note is userInitiated, which is a boolean property that
should be set if the request represents some action the user is waiting on. Setting this property to
true causes the underlying network task to be executed at a high priority and causes all
background queue processing to occur using QOS_CLASS_USER_INITIATED.

HTTPManagerUploadFormRequest provides support for creating multipart/form-data requests, which
can be used for uploading files/images. These requests are implemented in a streaming fashion, so
e.g. memory-mapped NSData objects won't be copied into a contiguous buffer, thus allowing you to
upload files without concerns about memory use.

HTTPManagerRequest conforms to NSCopying so copies can be made of any request if necessary.
Furthermore, when attaching a parse handler to a request (and therefore converting it into an
HTTPManagerParseRequest<T>) the original request data is copied so subsequent mutations to the
original request do not affect the parse request, and when a request is executed the request data is
copied so the request can be immediately mutated without affecting the executing network task.

Requests are also designed such that they can be easily created and executed using a
functional-style chain, as demonstrated by the Usage section above.

Parse requests always execute their parse handler on a background queue, with no option to run on a
given queue (or the main queue). This constraint exists both to encourage parsing in the background,
and for simplicity, as parsing on the main queue can always be accomplished by skipping the parse
handler and parsing in the completion block instead.

Request completion blocks are similarly executed on a background queue by default (for requests with
a parse handler, this will be the same queue that the parse handler executed on), although here a
specific queue can be provided where the completion block should run, such as the main queue.

Network Tasks

Executing a request returns a value of type HTTPManagerTask. This class is the PMHTTP equivalent
of URLSessionTask and is completely thread-safe. It provides properties for inspecting the
current state of the request, including for accessing the underlying URLSessionTask, and it
provides a cancel() method for canceling the request. Unlike URLSessionTask.cancel(),
HTTPManagerTask.cancel() can be used to cancel a request while the parse handler is executing, not
just canceling the networking portion. PMHTTP guarantees that if you execute
HTTPManagerTask.cancel() from the same queue that the completion block is targeting, prior to the
completion block itself executing, the completion block will always be given a result of .canceled
even if it had already finished parsing before cancel() was invoked. This means that if you target
the main queue for your completion block, you can be confident that a canceled task will never
behave as though it succeeded or failed.

Like URLSessionTask, HTTPManagerTask supports key-value observing (although, like
URLSessionTask, the KVO messages will occur on some background queue).

In the absence of automatic retrying, the networkTask property value will never change during the
lifetime of the task. If automatic retrying has been configured, networkTask will change if the
request is retried, and will broadcast any relevant key-value observing messages.

Network Activity Indicator

PMHTTP provides a callback you can use to implement support for the global network activity
indicator. Each request object has a property affectsNetworkActivityIndicator (which defaults to
true) that controls whether any tasks created from the request affect the callback. The callback
itself is configured by assigning a block to HTTPManager.networkActivityHandler. This block is run
on the main thread whenever the number of active tasks has changed. In order to display the global
network activity indicator you can configure this like so:

HTTPManager.networkActivityHandler = { active in
    UIApplication.sharedApplication().networkActivityIndicatorVisible = active > 0

Automatic Retrying of Failed Requests

PMHTTP includes support for automatically retrying failed requests according to a configurable
policy. The default retry policy can be configured with HTTPManager.defaultRetryBehavior, which
can be overridden on individual requests with HTTPManagerRequest.retryBehavior. A few common retry
policies are provided as convenience methods on HTTPManagerRetryBehavior, but any custom policy is
supported as well. The convenience policies implement intelligent handling of the various
NSURLErrorDomain errors, such as not retrying when encountering a non-transient error (such as
NSURLErrorAppTransportSecurityRequiresSecureConnection), or retrying non-idempotent requests if
the error indicates the server never received the request (e.g. NSURLErrorCannotConnectToHost). By
default, retrying is disabled.

Cache Handling

PMHTTP implements intelligent cache handling for JSON responses. The HTTP standard allows user
agents to cache responses at their discretion when the response does not include caching headers.
However, this behavior is inappropriate for most REST API requests, and URLSession does not
document its caching strategy for such responses. To handle this case, PMHTTP inspects JSON
responses for appropriate caching headers and explicitly prevents responses from being cached
if they do not include the appropriate cache directives. By default this behavior is only applied
to requests created with .parseAsJSON(), .parseAsJSON(using:), or .decodeAsJSON(_:), although
it can be overridden on a per-request basis (see
HTTPManagerRequest.defaultResponseCacheStoragePolicy). Notably, requests created with
.parse(using:) do not use this cache strategy as it would interfere with caching image requests.


PMHTTP has built-in support for mocking network requests. This is done without swizzling (so it's
safe to mock requests even in App Store builds), and it's done in a fashion that still creates a
valid URLSessionTask (so any code that inspects HTTPManagerTask.networkTask will function as
expected). Mocks can be registered on the HTTPManager as a whole, and individual requests can be
independently mocked (so you can control whether a request is mocked based on more than just the URL
in question).


PMHTTP itself has a comprehensive test suite, covering just about everything in the Swift API (the
Obj-C–specific API is not currently tested, see
issue #7). The tests are run against a custom
HTTP/1.1 server implemented in the test bundle that listens on the loopback interface. This allows
for testing all the functionality without any dependencies on external services and ensures the
tests are very fast. The HTTP/1.1 server currently relies on CocoaAsyncSocket, which can be
installed with carthage bootstrap. This dependency is not exposed to clients of PMHTTP as it's
only used by the test suite.

The HTTP/1.1 server implements just about everything that I thought was useful. It has a few minor
dependencies on PMHTTP itself (most notably, it uses HTTPManagerRequest.HTTPHeaders instead of
reimplementing the functionality), but beyond that, it could actually be pulled out and used
anywhere else that an HTTP/1.1 server is required. However, as this server was written for the
purposes of testing and not production use, it does not have any built-in mitigation of DOS attacks
beyond rejecting uploads greater than 5MiB (for example, it does not impose any limit on headers,
which are kept in memory, and it does not have any sort of timeout on connection duration). It also
does not have any tests itself, beyond the fact that it behaves as expected when used in the PMHTTP
test suite.


Requires a minimum of iOS 8, macOS 10.10, watchOS 2.0, or tvOS 9.0.


After installation with any mechanism, you can use this by adding import PMHTTP to your code.


To install using Carthage, add the following to your Cartfile:

github "postmates/PMHTTP" ~> 4.0

This release supports Swift 4.0. For Swift 3.x you can use

github "postmates/PMHTTP" ~> 3.0


To install using CocoaPods, add the following to your Podfile:

pod "PMHTTP", "~> 4.0"

This release supports Swift 4.0. For Swift 3.x you can use:

pod "PMHTTP", "~> 3.0"


Licensed under either of


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the
work by you shall be dual licensed as above, without any additional terms or conditions.

Version History

v4.5.0 (2019-11-27)

  • Add Obj-C convenience functions for creating upload requests with an NSData but no explicit contentType (#65).
  • Fix the Obj-C -setValue:forHeaderField: and -setValue:forDefaultHeaderField: methods to take a nullable value (#67).
  • Add HTTPManagerRetryBehavior.init(any:) to combine multiple retry behaviors together (#69).
  • Add HTTPManagerRequest.HTTPHeaders methods init(minimumCapacity:) and reserveCapacity(_:) and property capacity (#66).

v4.4.3 (2019-11-14)

  • Support PMJSON 4.x in addition to PMJSON 3.x with CocoaPods. Carthage doesn't support that kind of version range so it's now just set to PMJSON 4.x only.

v4.4.2 (2019-08-13)

  • Fix a bug with the deprecated HTTPManagerObjectParseRequest.credential property where assigning to the property wouldn't work.

v4.4.1 (2019-04-24)

v4.4.0 (2019-04-23)

  • Fix a bug when parsing images where we passed the wrong value for the type identifier hint, resulting in a warning being logged to the console (#62).
  • Add computed properties on HTTPManagerError for convenient access to the associated values (e.g. .response, .body, etc).
  • Add computed property HTTPManagerError.statusCode that returns the failing status code for the error, or nil for .unexpectedContentType (#60).
  • Add Obj-C function PMHTTPErrorGetStatusCode() that returns the failing status code for the error, or nil for PMHTTPErrorUnexpectedContentType or for non-PMHTTP errors (#60).
  • Provide PMHTTPStatusCodeErrorKey user info key for more error types (#59).
  • Add computed property URLResponse.isUnmockedInterceptedRequest that can be used to test if a response comes from a request that was intercepted by the mock manager without a mock installed (#46).

v4.3.3 (2019-04-07)

  • Update PMHTTPErrorIsFailedResponse to handle PMHTTPErrorUnexpectedNoContent and PMHTTPErrorUnexpectedRedirect in addition to PMHTTPErrorFailedResponse and PMHTTPErrorUnauthorized.
  • Fix warnings introduced by Xcode 10.2.

v4.3.2 (2018-11-14)

  • Fix bug where requests constructed from a URL would not inherit environmental defaults (e.g. auth, headers, etc) (#52).

v4.3.1 (2018-08-01)

  • Add URLProtocol method overloads to query and set protocol properties on HTTPManagerRequests (#43).

v4.3.0 (2018-07-26)

  • Expose HTTPManagerTask.userInitiated as a public property (#42).
  • Add another parameter to the HTTPManager.MetricsCallback callback. In order to retain backwards compatibility, the old initializer and property were deprecated and a new initializer and property were added with different names (#41).

v4.2.0 (2018-07-10)

  • Percent-encode more characters for application/x-www-form-urlencoded bodies and query strings. Notably, semicolon (;) is now percent-encoded, as some servers treat it as a separator.
  • Optimize task metrics collection such that metrics are not collected if metricsCallback is nil (#37).
  • Extend built-in retry behaviors to support custom strategies (#35).
  • Add HTTPManagerRequest properties that correspond to the URLRequest properties mainDocumentURL and httpShouldHandleCookies (#40).

v4.1.1 (2018-06-21)

  • Add HTTPHeaders.merge(_:uniquingKeysWith:) and HTTPHeaders.merging(_:uniquingKeysWith:).
  • Deprecate HTTPHeaders.append(contentsOf:).
  • Merge header fields when calling HTTPManagerRequest.setDefaultEnvironmentalProperties(), giving priority to existing request header fields in the case
    of a conflict.

v4.1.0 (2018-06-15)

  • Support mocking relative URLs when no environment has been set.
  • Shrink the default mock delay to 10ms.
  • Make HTTPManagerRequest.headerFields mutable in Obj-C.
  • Add HTTPManager.defaultHeaderFields which defines the default header fields to attach to requests and, like defaultAuth, only applies to requests within the current environment.
  • Declare conformance to Equatable for HTTPManagerRequest.HTTPHeaders.
  • Fix fatal error when using deferred multipart bodies along with serverRequiresContentLength.
  • Add HTTPManager.metricsCallback to collect task metrics (URLSessionTaskMetrics) from all tasks associated with the HTTPManager.

v4.0.1 (2018-05-17)

  • Fix <PMHTTP/PMHTTP.h> so it can be imported from Obj-C++ code.

v4.0.0 (2018-02-23)

  • Convert to Swift 4.
  • Add a method
  • Add methods HTTPManagerDataRequest.decodeAsJSON(_:with:options:) and HTTPManagerActionRequest.decodeAsJSON(_:with:options:).

v3.0.5 (2017-09-11)

  • Extend HTTPAuth to support handling 403 Forbidden errors as well.

v3.0.4 (2017-09-05)

  • Support Swift 3.2.
  • Handle serverRequiresContentLength correctly in preparedURLRequest.

v3.0.3 (2017-08-18)

  • Add overloads to the request creation methods that take a URL. These overloads return a non-optional request.
  • Add new property HTTPManagerRequest.serverRequiresContentLength. This disables streaming body support (for JSON and multipart/mixed) and instead encodes the body synchronously so it can provide a "Content-Length" header to the server. There is a corresponding HTTPManager.defaultServerRequiresContentLength property as well.
  • Add a method HTTPManagerRequest.setDefaultEnvironmentalProperties() that sets properties to the HTTPManager-defined defaults that otherwise are only set if the request's path matches the environment. This is primarily intended for requests constructed using absolute paths (e.g. HTTP.request(GET: "/foo")) that should still use the environment defaults. Right now this method only sets auth and serverRequiresContentLength.

v3.0.2 (2017-05-01)

  • Add @discardableResult to Obj-C -performRequest… methods.

v3.0.1 (2017-03-28)

  • Fix Xcode 8.3 compatibility.

v3.0.0 (2017-02-27)

  • Preserve network task priority when retrying tasks.
  • Add convenience Obj-C function PMHTTPErrorIsFailedResponse to test PMHTTP errors easily.
  • Add methods .parseAsImage(scale:) and .parseAsImage(scale:using:) to HTTPManagerDataRequest and HTTPManagerActionRequest.
  • When a session is reset, cancel any tasks that were created but never resumed.
  • Ensure that the completion block is always deallocated on either the completion queue or on the thread that created the task. Previously there was a very subtle race that meant the completion block could deallocate on the URLSession's delegate queue instead. This only matters if your completion block captures values whose deinit cares about the current thread.
  • Expand dictionaries, arrays, and sets passed as parameters. Dictionaries produce keys of the form "foo[bar]" and arrays and sets just use the key multiple times (e.g. "foo=bar&foo=qux"). The expansion is recursive. The order of values from expanded dictionaries and sets is implementation-defined. If you want "array[]" syntax, then put the "[]" in the key itself. See the documentation comments for more details. Do note that this behavior is slightly different from what AFNetworking does.
  • Also expand nested URLQueryItems in parameters. The resulting parameter uses dictionary syntax ("foo[bar]").
  • Change the type signature of the Obj-C parse methods that take handlers to make the error parameter non-optional.
  • Provide a callback that can be used for session-level authentication challenges. This can be used to implement SSL pinning using something like TrustKit.
  • Fix a small memory leak when retrying tasks.
  • Rework how authorization works. The defaultCredential and credential properties have been replaced with defaultAuth and auth, using a brand new protocol HTTPAuth. An implementation of Basic authentication is provided with the HTTPBasicAuth object. This new authentication mechanism has been designed to allow for OAuth2-style refreshes, and a helper class HTTPRefreshableAuth is provided to make it easy to implement refreshable authentication.

v2.0.1 (2017-01-05)

  • Fix PMJSON dependency in CocoaPods podspec.

v2.0.0 (2017-01-03)

  • Support text/json in addition to application/json.
  • Add 2 convenience methods for uploading UIImages as PNG or JPEG data.
  • Add objcError property to PMHTTPResult.
  • Change objcError on HTTPManagerTaskResult to Error? instead of NSError?.
  • Fix Xcode 8.1 compatibility of unit tests.
  • Add optional options parameter to parseAsJSON() and parseAsJSON(with:).
  • Add withMultipartBody(using:) to HTTPManagerUploadFormRequest.
  • Rename parse(with:), parseAsJSON(options:with:), and addMultipartBody(with:) to use the parameter name using: instead, which is more in line with Swift 3 Foundation naming conventions.

v1.0.4 (2016-10-20)

  • Add more Obj-C request constructors.
  • Fix encoding of + characters in query strings and application/x-www-form-urlencoded bodies.

v1.0.3 (2016-09-23)

  • Fix obj-c name of HTTPManager.parsedDateHeader(from:).

v1.0.2 (2016-09-22)

  • Add fix-its for the Swift 3 API changes.

v1.0.1 (2016-09-12)

  • Adopt CustomNSError and deprecate the NSError bridging methods.
  • Add autoreleasepools to dispatch queues where appropriate.
  • Fix CocoaPods support.

v1.0.0 (2016-09-09)

  • Support Swift 3.0.

v0.9.3 (2016-09-09)

  • Fix building for tvOS.

v0.9.2 (2016-09-09)

  • Support Swift 2.3.

v0.9.1 (2016-08-17)

  • Rename Source folder to Sources.
  • CocoaPods support.

v0.9 (2016-08-05)

Initial release.