pecker is a tool to automatically detect unused code. It based on IndexStoreDB and SwiftSyntax.

Why use this?

During the project development process, you may write a lot of code. Over time, a lot of code is no longer used, but it is difficult to find. pecker can help you locate these unused code conveniently and accurately.


pecker can detect the following kinds of unused Swift code.

  1. class
  2. struct
  3. enum
  4. protocol
  5. function
  6. typealias
  7. operator


$ git clone
$ cd Pecker
$ make install

With that installed and on our bin folder, now we can use it.



  1. Click on your project in the file list, choose your target under TARGETS, click the Build Phases tab and add a New Run Script Phase by clicking the little plus icon in the top left.
  2. Paste the following script:


Command Line Usage

pecker [OPTIONS]

  • -v/--version: Prints the pecker version and exits.
  • -i/--index-store-path: The Index path of your project, if unspecified, the default is ~Library/Developer/Xcode/DerivedData/<target>/Index/DataStore.

Run pecker in the project target to detect. Project will be searched Swift files recursively.


Current only 2 rules are included in Pecker, They are skip_public and xctest, You can also check Source/PeckerKit/Rules directory to see their implementation.


This rule means skip detect public class, struct, function, etc. Usually the public code is provided for other users, so it is difficult to determine whether it is used. So we don't detect it by default. But in some cases, such as using submodule to organize code, you need to detect public code, you can add it to disabled_rules.


XCTest is special, we stipulate that ignore classes inherited from XCTestCase and functions of this class that hasPrefix "test" and do not contain parameters. You can add it to disabled_rules if you don't need it.

class ExampleUITests: XCTestCase {

    func testExample() { //used

    func test(name: String) { // unused
    func get() { // unsed

Other rules

These rules are used by default, you cannot configure them.


Skip declarations that override another. This works for both subclass overrides & protocol extension overrides.

protocol ExampleProtocol {
	func test() // used

class Example: ExampleProtocol {
    func test() { // used

class Animal {
    func run() {  // used

class Dod: Animal {
    override func run() { // used


Referenced elsewhere means used, except for extensions.

class UnusedExample { // unused

extension UnusedExample {


Configure pecker by adding a .pecker.yml file from the directory you'll
run pecker from. The following parameters can be configured:

Rule inclusion:

  • disabled_rules: Disable rules from the default enabled set.

Reporter inclusion:

  • xcode: Warnings displayed in the IDE.
  • json: Generate a warnings json file.
reporter: "xcode"

  - skip_public

included: # paths to include during detecting. `--path` is ignored if present.
  - ./
excluded: # paths to ignore during detecting. Takes precedence over `included`.
  - Carthage
  - Pods

blacklist_files: # files to ignore during detecting, only need to add file name, the file extension default is swift.
  - HomeViewController

blacklist_symbols: # symbols to ignore during detecting, contains class, struct, enum, etc.
  - AppDelegate
  - viewDidLoad