Swift package for easily rendering text tables

by iOS Example

TextTable




Easily print textual tables in Swift. Inspired by the Python tabulate library.

Upcoming Changes

See details on an upcoming change.

Features

  • Easily generate textual tables from collections of any type
  • Auto-calculates column width
  • Custom width for individual columns
  • Align individual columns
  • Supports per-column Formatters
  • Multiple table output styles including Markdown, Emacs, HTML, Latex etc...
  • Extensible table styles allow you to easily create your own table style
  • Column-specific truncation modes (truncate head or tail of column content or optionally fail if content overflows).

Requirements

This package was written for and tested with the following version of Swift:

Apple Swift version 5.0

Usage

Use the Swift Package Manager to install TextTable as a dependency of your project.

dependencies: [
    .package(
        url: "https://github.com/cfilipov/TextTable",
        .branch("master"))
]

First, import TextTable:

import TextTable

Throughout the examples, the following data structure will be used:

struct Person {
    let name: String
    let age: Int
    let birhtday: Date
}

Let's say we have a collection of Person we wish to display as a table.

let data = [
	Person(name: "Alice", age: 42, birhtday: Date()),
	Person(name: "Bob", age: 22, birhtday: Date()),
	Person(name: "Eve", age: 142, birhtday: Date())
]

Configure a TextTable Instance

Configure a TextTable instance for the type you wish to print as a table. The minimum configuration will require a mapping of values to columns for your type.

let table = TextTable<Person> {
    [Column("Name" <- $0.name),
     Column("Age" <- $0.age),
     Column("Birthday" <- $0.birhtday)]
}

Alternate Syntax

The <- operator is just syntactic sugar. If you don't want to use the operator, you can use labeled arguments instead.

let table = TextTable<Person> {
    [Column(title: "Name", value: $0.name),
     Column(title: "Age", value: $0.age),
     Column(title: "Birthday", value: $0.birhtday)]
}

Printing a Table

Simply call the print() method, passing in a collection of Person.

table.print(data)

Name  Age Birthday
----- --- -------------------------
Alice 42  2016-08-13 19:21:54 +0000
Bob   22  2016-08-13 19:21:54 +0000
Eve   142 2016-08-13 19:21:54 +0000

Getting a String

You can also just get the rendered table as a string by calling the string(for:) method.

let s = table.string(for: data)

Customize Table Style

You can optionally specify a table style using the style: argument.

table.print(data, style: Style.psql)

+-------+-----+---------------------------+
| Name  | Age | Birthday                  |
+-------+-----+---------------------------+
| Alice | 42  | 2016-08-13 08:12:58 +0000 |
| Bob   | 22  | 2016-08-13 08:12:58 +0000 |
| Eve   | 142 | 2016-08-13 08:12:58 +0000 |
+-------+-----+---------------------------+

The style can also be specified when using the string(for:) method.

let s = table.string(for: data, style: Style.psql)

For a full list of supported styles see Supported Styles below.

Column-Specific Formatters

You can specify a Formatter on a per-column basis. In this example a DateFormatter is used to customize the display of the Birthday column.

let df = DateFormatter()
dateFormatter.dateStyle = .medium

let table = TextTable<Person> {
    [Column("Name" <- $0.name),
     Column("Age" <- $0.age),
     Column("Birthday" <- $0.birhtday, formatter: df)]
}

table.print(data, style: Style.psql)

+-------+-----+--------------+
| Name  | Age | Birthday     |
+-------+-----+--------------+
| Alice | 42  | Aug 13, 2016 |
| Bob   | 22  | Aug 13, 2016 |
| Eve   | 142 | Aug 13, 2016 |
+-------+-----+--------------+

Column Width

By default TextTable will calculate the necessary width for each column. You can also explictely set the width with the width: argument.

let table = TextTable<Person> {
    [Column("Name" <- $0.name, width: 10),
     Column("Age" <- $0.age, width: 10)]
}

table.print(data, style: Style.psql)

+------------+------------+
| Name       | Age        |
+------------+------------+
| Alice      | 42         |
| Bob        | 22         |
| Eve        | 142        |
+------------+------------+

Note on Padding

Some table styles may include padding to the left and/or right of the content, the width argument does not effect include this padding.

Truncation

Truncate Tail

By default, if a width is specified and the contents of the column are wider than the width, the text will be truncated at the tail (.tail truncation mode).

let table = TextTable<Person> {
	[Column("Name" <- $0.name, width: 4), // defaults to truncation: .tail
	 Column("Age" <- $0.age)]
}

table.print(data, style: testStyle)

+------+-----+
| Name | Age |
+------+-----+
| Ali… | 42  |
| Bob  | 22  |
| Eve  | 142 |
+------+-----+

Truncate Head

You can also truncate at the head of the text string by specifying .head for the truncation: argument. If no width argument is present, the truncation argument has no effect.

let table = TextTable<Person> {
	[Column("Name" <- $0.name, width: 4, truncate: .head),
	 Column("Age" <- $0.age)]
}

table.print(data, style: testStyle)

+------+-----+
| Name | Age |
+------+-----+
| …ice | 42  |
| Bob  | 22  |
| Eve  | 142 |
+------+-----+

Truncate Error

If you prefer to have an fatal error triggered when the contents of a column do not fit the specified width you can specify the .error truncation mode.

let table = TextTable<Person> {
	[Column("Name" <- $0.name, width: 4, truncate: .error),
	 Column("Age" <- $0.age)]
}

table.print(data, style: testStyle)

// fatal error: Truncation error

Column Alignment

By default, all columns will be left-aligned. You can set the alignment on each column individually.

let table = TextTable<Person> {
    [Column("Name" <- $0.name), // default: .left
     Column("Age" <- $0.age, align: .right)]
}

table.print(data, style: Style.psql)

+-------+-----+
| Name  | Age |
+-------+-----+
| Alice |  42 |
| Bob   |  22 |
| Eve   | 142 |
+-------+-----+

Performance Characteristics

By default TextTable will calculate the necessary width for each column that does not specify an explicit width using the width: column argument. This calculation is accomplished by iterating over each row of the table twice: the first time to calculate the max width, the second time to actually render the table. The overhead of this calculation may not be appropriate for very large tables. If you wish to avoid this calculation you must specify the width for every column.

In the example below table1 will incur the overhead of the width calculation because one of the columns does not have an explicit width. On the other hand, table2 will not incur the overhead because all columns have an explicit width.

// This will still result in extra calculations
let table1 = TextTable<Person> {
    [Column("Name" <- $0.name),
     Column("Age" <- $0.age, width: 10)]
}

// This will skip the width calculations
let table2 = TextTable<Person> {
    [Column("Name" <- $0.name, width: 9),
     Column("Age" <- $0.age, width: 10)]
}

Supported Styles

TextTable supports most of the styles as tabulate.

Plain

table.print(data, style: Style.plain)

Name  Age Birthday
Alice  42  8/13/16
Bob    22  8/13/16
Eve   142  8/13/16

Simple

simple is the default Style. It corresponds to simple_tables in Pandoc Markdown extensions.

table.print(data) // or:
table.print(data, style: Style.simple)

Name  Age Birthday
----- --- --------
Alice  42  8/13/16
Bob    22  8/13/16
Eve   142  8/13/16

Grid

grid follows the conventions of Emacs’ table.el package. It corresponds to grid_tables in Pandoc Markdown extensions.

table.print(data, style: Style.grid)

+-------+-----+----------+
| Name  | Age | Birthday |
+=======+=====+==========+
| Alice |  42 |  8/13/16 |
+-------+-----+----------+
| Bob   |  22 |  8/13/16 |
+-------+-----+----------+
| Eve   | 142 |  8/13/16 |
+-------+-----+----------+

FancyGrid

table.print(data, style: Style.fancyGrid)

╒═══════╤═════╤══════════╕
│ Name  │ Age │ Birthday │
╞═══════╪═════╪══════════╡
│ Alice │  42 │  8/13/16 │
├───────┼─────┼──────────┤
│ Bob   │  22 │  8/13/16 │
├───────┼─────┼──────────┤
│ Eve   │ 142 │  8/13/16 │
╘═══════╧═════╧══════════╛

Psql

table.print(data, style: Style.psql)

+-------+-----+----------+
| Name  | Age | Birthday |
+-------+-----+----------+
| Alice |  42 |  8/13/16 |
| Bob   |  22 |  8/13/16 |
| Eve   | 142 |  8/13/16 |
+-------+-----+----------+

Pipe

pipe follows the conventions of PHP Markdown Extra extension. It corresponds to pipe_tables in Pandoc. This style uses colons to indicate column alignment.

table.print(data, style: Style.pipe)

| Name  | Age | Birthday |
|:------|----:|---------:|
| Alice |  42 |  8/13/16 |
| Bob   |  22 |  8/13/16 |
| Eve   | 142 |  8/13/16 |

Org

org follows the conventions of Emacs org-mode.

table.print(data, style: Style.org)

| Name  | Age | Birthday |
|-------+-----+----------|
| Alice |  42 |  8/13/16 |
| Bob   |  22 |  8/13/16 |
| Eve   | 142 |  8/13/16 |

Rst

rst follows the conventions of simple table of the reStructuredText Style.

table.print(data, style: Style.rst)

===== === ========
Name  Age Birthday
===== === ========
Alice  42  8/13/16
Bob    22  8/13/16
Eve   142  8/13/16
===== === ========

Html

html produces HTML table markup.

table.print(data, style: Style.html)

<table>
    <tr>
        <th style="text-align:left;">Name</th>
        <th style="text-align:center;">Age</th>
        <th style="text-align:right;">Birthday</th>
    </tr>
    <tr>
        <td>Alice</td>
        <td>42</td>
        <td>8/14/16</td>
    </tr>
    <tr>
        <td>Bob</td>
        <td>22</td>
        <td>8/14/16</td>
    </tr>
    <tr>
        <td>Eve</td>
        <td>142</td>
        <td>8/14/16</td>
    </tr>
</table>

Latex

latex produces a tabular environment for Latex.

table.print(data, style: Style.latex)

\begin{tabular}{lll}
\hline
 Name & Age & Birthday \\
\hline
 Alice & 42 & 8/13/16 \\
 Bob & 22 & 8/13/16 \\
 Eve & 142 & 8/13/16 \\
\hline
\end{tabular}

Custom Styles

You can create a custom table style by conforming to the TextTableStyle protocol.

enum MyCustomStyle: TextTableStyle {
    // implement methods from TextTableStyle...
}

extension Style {
    static let custom = MyCustomStyle.self
}

table.print(data, style: Style.custom)

Alternatives

Other Swift libraries that serve a similar purpose.

License

MIT License

Copyright (c) 2016 Cristian Filipov

GitHub

https://github.com/cfilipov/TextTable