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realm /SwiftLint

A tool to enforce Swift style and conventions.

13.6K Stars 1.6K Forks Last release: 3 months ago (0.39.2) MIT License 4.9K Commits 75 Releases

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A tool to enforce Swift style and conventions, loosely based onGitHub's Swift Style Guide.

SwiftLint hooks into Clang andSourceKit to use theAST representation of your source files for more accurate results.


This project adheres to the Contributor Covenant Code of Conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to [email protected].

Language Switch: 中文, 한국어.


Using Homebrew:

brew install swiftlint

Using CocoaPods:

Simply add the following line to your Podfile:

pod 'SwiftLint'

This will download the SwiftLint binaries and dependencies in


during your next

pod install

execution and will allow you to invoke it via


in your Script Build Phases.

This is the recommended way to install a specific version of SwiftLint since it supports installing a pinned version rather than simply the latest (which is the case with Homebrew).

Note that this will add the SwiftLint binaries, its dependencies' binaries and the Swift binary library distribution to the


directory, so checking in this directory to SCM such as git is discouraged.

Using Mint:

$ mint install realm/SwiftLint

Using a pre-built package:

You can also install SwiftLint by downloading


from thelatest GitHub release and running it.

Compiling from source:

You can also build from source by cloning this project and running

git submodule update --init --recursive; make install

(Xcode 10.2 or later).

Known Installation Issues On MacOS Before 10.14.4

Starting with SwiftLint 0.32.0, if you get an error similar to

dyld: Symbol not found: \_$s11SubSequenceSlTl

when running SwiftLint, you'll need to install the Swift 5 Runtime Support for Command Line Tools.

Alternatively, you can:

  • Update to macOS 10.14.4 or later
  • Install Xcode 10.2 or later at
  • Rebuild SwiftLint from source using Xcode 10.2 or later



To get a high-level overview of recommended ways to integrate SwiftLint into your project, we encourage you to watch this presentation or read the transcript:



Integrate SwiftLint into an Xcode scheme to get warnings and errors displayed in the IDE. Just add a new "Run Script Phase" with:

if which swiftlint \>/dev/null; then swiftlint else echo "warning: SwiftLint not installed, download from" fi

Alternatively, if you've installed SwiftLint via CocoaPods the script should look like this:


Format on Save Xcode Plugin

To run

swiftlint autocorrect

on save in Xcode, install theSwiftLintXcode plugin from Alcatraz.

⚠️This plugin will not work with Xcode 8 or later without disabling SIP. This is not recommended.


To integrate SwiftLint with AppCode, installthis plugin and configure SwiftLint's installed path in the plugin's preferences. The


action is available via




To integrate SwiftLint with Atom, install the[


]( package from APM.


You can use the official swiftlint fastlane action to run SwiftLint as part of your fastlane process.

swiftlint( mode: :lint, # SwiftLint mode: :lint (default) or :autocorrect executable: "Pods/SwiftLint/swiftlint", # The SwiftLint binary path (optional). Important if you've installed it via CocoaPods path: "/path/to/lint", # Specify path to lint (optional) output\_file: "swiftlint.result.json", # The path of the output file (optional) reporter: "json", # The custom reporter to use (optional) config\_file: ".swiftlint-ci.yml", # The path of the configuration file (optional) files: [# List of files to process (optional) "AppDelegate.swift", "path/to/project/Model.swift"], ignore\_exit\_status: true, # Allow fastlane to continue even if SwiftLint returns a non-zero exit status (Default: false) quiet: true, # Don't print status logs like 'Linting ' & 'Done linting' (Default: false) strict: true # Fail on warnings? (Default: false) )

Command Line

$ swiftlint help Available commands: analyze [Experimental] Run analysis rules autocorrect Automatically correct warnings and errors generate-docs Generates markdown documentation for all rules help Display general or command-specific help lint Print lint warnings and errors (default command) rules Display the list of rules and their identifiers version Display the current version of SwiftLint



in the directory containing the Swift files to lint. Directories will be searched recursively.

To specify a list of files when using






(like the list of files modified by Xcode specified by the[


]( Xcode plugin, or modified files in the working tree based on

git ls-files -m

), you can do so by passing the option


and setting the following instance variables:









These are same environment variables set for input files tocustom Xcode script phases.

Working With Multiple Swift Versions

SwiftLint hooks into SourceKit so it continues working even as Swift evolves!

This also keeps SwiftLint lean, as it doesn't need to ship with a full Swift compiler, it just communicates with the official one you already have installed on your machine.

You should always run SwiftLint with the same toolchain you use to compile your code.

You may want to override SwiftLint's default Swift toolchain if you have multiple toolchains or Xcodes installed.

Here's the order in which SwiftLint determines which Swift toolchain to use:

  • xcrun -find swift
  • /Applications/
  • /Applications/
  • ~/Applications/
  • ~/Applications/

is expected to be found in the


subdirectory of the value passed in the paths above.

You may also set the


environment variable to the reverse-DNS notation that identifies a Swift toolchain version:

$\_2\_3 swiftlint autocorrect

On Linux, SourceKit is expected to be located in


or specified by the


environment variable.

Swift Version Support

Here's a reference of which SwiftLint version to use for a given Swift version.

| Swift version | Last supported SwiftLint release | |:----------------|:---------------------------------| | Swift 1.x | SwiftLint 0.1.2 | | Swift 2.x | SwiftLint 0.18.1 | | Swift 3.x | SwiftLint 0.25.1 | | Swift 4.0-4.1.x | SwiftLint 0.28.2 | | Swift 4.2.x | SwiftLint 0.35.0 | | Swift 5.x | Latest |


Over 75 rules are included in SwiftLint and the Swift community (that's you!) continues to contribute more over time.Pull requests are encouraged.

You can find an updated list of rules and more information about themhere.

You can also check Source/SwiftLintFramework/Rulesdirectory to see their implementation.

Opt-In Rules


are disabled by default (i.e., you have to explicitly enable them in your configuration file).

Guidelines on when to mark a rule as opt-in:

  • A rule that can have many false positives (e.g.
  • A rule that is too slow
  • A rule that is not general consensus or is only useful in some cases (e.g.

Disable rules in code

Rules can be disabled with a comment inside a source file with the following format:

// swiftlint:disable <rule1> [<rule2> <rule3>...]</rule3></rule2></rule1>

The rules will be disabled until the end of the file or until the linter sees a matching enable comment:

// swiftlint:enable <rule1> [<rule2> <rule3>...]</rule3></rule2></rule1>

For example:

// swiftlint:disable colon let noWarning :String = "" // No warning about colons immediately after variable names! // swiftlint:enable colon let hasWarning :String = "" // Warning generated about colons immediately after variable names

Including the


keyword will disable all rules until the linter sees a matching enable comment:

// swiftlint:disable all
// swiftlint:enable all

For example:

// swiftlint:disable all let noWarning :String = "" // No warning about colons immediately after variable names! let i = "" // Also no warning about short identifier names // swiftlint:enable all let hasWarning :String = "" // Warning generated about colons immediately after variable names let y = "" // Warning generated about short identifier names

It's also possible to modify a




command by appending






for only applying the command to the previous, this (current) or next line respectively.

For example:

// swiftlint:disable:next force\_cast let noWarning = NSNumber() as! Int let hasWarning = NSNumber() as! Int let noWarning2 = NSNumber() as! Int // swiftlint:disable:this force\_cast let noWarning3 = NSNumber() as! Int // swiftlint:disable:previous force\_cast


swiftlint rules

to print a list of all available rules and their identifiers.


Configure SwiftLint by adding a


file from the directory you'll run SwiftLint from. The following parameters can be configured:

Rule inclusion:

  • disabled\_rules
    : Disable rules from the default enabled set.
  • opt\_in\_rules
    : Enable rules not from the default set.
  • whitelist\_rules
    : Acts as a whitelist, only the rules specified in this list will be enabled. Can not be specified alongside
  • analyzer\_rules
    : This is an entirely separate list of rules that are only run by the
    command. All analyzer rules are opt-in, so this is the only configurable rule list (there is no disabled/whitelist equivalent).
disabled\_rules: # rule identifiers to exclude from running - colon - comma - control\_statement opt\_in\_rules: # some rules are only opt-in - empty\_count # Find all the available rules by running: # swiftlint rules included: # paths to include during linting. `--path` is ignored if present. - Source excluded: # paths to ignore during linting. Takes precedence over `included`. - Carthage - Pods - Source/ExcludedFolder - Source/ExcludedFile.swift - Source/\*/ExcludedFile.swift # Exclude files with a wildcard analyzer\_rules: # Rules run by `swiftlint analyze` (experimental) - explicit\_self # configurable rules can be customized from this configuration file # binary rules can set their severity level force\_cast: warning # implicitly force\_try: severity: warning # explicitly # rules that have both warning and error levels, can set just the warning level # implicitly line\_length: 110 # they can set both implicitly with an array type\_body\_length: - 300 # warning - 400 # error # or they can set both explicitly file\_length: warning: 500 error: 1200 # naming rules can set warnings/errors for min\_length and max\_length # additionally they can set excluded names type\_name: min\_length: 4 # only warning max\_length: # warning and error warning: 40 error: 50 excluded: iPhone # excluded via string allowed\_symbols: ["\_"] # these are allowed in type names identifier\_name: min\_length: # only min\_length error: 4 # only error excluded: # excluded via string array - id - URL - GlobalAPIKey reporter: "xcode" # reporter type (xcode, json, csv, checkstyle, junit, html, emoji, sonarqube, markdown)

You can also use environment variables in your configuration file, by using


in a string.

Defining Custom Rules

You can define custom regex-based rules in your configuration file using the following syntax:

custom\_rules: pirates\_beat\_ninjas: # rule identifier included: ".\*\\.swift" # regex that defines paths to include during linting. optional. excluded: ".\*Test\\.swift" # regex that defines paths to exclude during linting. optional name: "Pirates Beat Ninjas" # rule name. optional. regex: "([n,N]inja)" # matching pattern capture\_group: 0 # number of regex capture group to highlight the rule violation at. optional. match\_kinds: # SyntaxKinds to match. optional. - comment - identifier message: "Pirates are better than ninjas." # violation message. optional. severity: error # violation severity. optional. no\_hiding\_in\_strings: regex: "([n,N]inja)" match\_kinds: string

This is what the output would look like:

You can filter the matches by providing one or more


, which will reject matches that include syntax kinds that are not present in this list. Here are all the possible syntax kinds:

  • argument
  • attribute.builtin
  • buildconfig.keyword
  • comment
  • comment.mark
  • comment.url
  • doccomment
  • doccomment.field
  • identifier
  • keyword
  • number
  • objectliteral
  • parameter
  • placeholder
  • string
  • string_interpolation_anchor
  • typeidentifier

If using custom rules alongside a whitelist, make sure to add


as an item under



Nested Configurations

SwiftLint supports nesting configuration files for more granular control over the linting process.

  • Include additional
    files where necessary in your directory structure.
  • Each file will be linted using the configuration file that is in its directory or at the deepest level of its parent directories. Otherwise the root configuration will be used.
  • included
    is ignored for nested configurations.


SwiftLint can automatically correct certain violations. Files on disk are overwritten with a corrected version.

Please make sure to have backups of these files before running

swiftlint autocorrect

, otherwise important data may be lost.

Standard linting is disabled while correcting because of the high likelihood of violations (or their offsets) being incorrect after modifying a file while applying corrections.

Analyze (experimental)

The experimental

swiftlint analyze

command can lint Swift files using the full type-checked AST. The compiler log path containing the clean


build command invocation (incremental builds will fail) must be passed to


via the


flag. e.g.

--compiler-log-path /path/to/xcodebuild.log

This can be obtained by running

xcodebuild -workspace {WORKSPACE}.xcworkspace -scheme {SCHEME} \> xcodebuild.log

with a clean



This command and related code in SwiftLint is subject to substantial changes at any time while this feature is marked as experimental. Analyzer rules also tend to be considerably slower than lint rules.


MIT licensed.


SwiftLint is maintained and funded by Realm Inc. The names and logos for Realm are trademarks of Realm Inc.

We :heart: open source software! See our other open source projects, read our blog, or say hi on twitter (@realm).

Our thanks to MacStadium for providing a Mac Mini to run our performance tests.

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