A tool to enforce Swift style and conventions, loosely based on GitHub's Swift Style Guide.
brew install swiftlint
Simply add the following line to your Podfile:
This will download the SwiftLint binaries and dependencies in
Pods/ 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
Pods/ directory, so checking in this directory to SCM such as
git is discouraged.
Using a pre-built package:
You can also install SwiftLint by downloading
SwiftLint.pkg from the
latest GitHub release and
Compiling from source:
You can also build from source by cloning this project and running
git submodule update --init --recursive; make install (Xcode 8.0 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 https://github.com/realm/SwiftLint" fi
Alternatively, if you've installed SwiftLint via CocoaPods the script should look like this:
Format on Save Xcode Plugin
swiftlint autocorrect on save in Xcode, install the
SwiftLintXcode plugin from Alcatraz.
⚠ ️This plugin will not work with Xcode 8 without diabling SIP. This is not recommended.
To integrate SwiftLint with AppCode, install
this plugin and configure
SwiftLint's installed path in the plugin's preferences.
autocorrect action is available via
$ swiftlint help Available commands: autocorrect Automatically correct warnings and errors help Display general or command-specific help lint Print lint warnings and errors for the Swift files in the current directory (default command) rules Display the list of rules and their identifiers version Display the current version of SwiftLint
swiftlint in the directory containing the Swift files to lint. Directories
will be searched recursively.
To specify a list of files when using
autocorrect (like the list of
files modified by Xcode specified by the
plugin, or modified files in the working tree based on
git ls-files -m), you
can do so by passing the option
--use-script-input-files and setting the
following instance variables:
These are same environment variables set for input files to custom 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, or if you're using legacy Swift versions (e.g. Swift 2.3 with Xcode 8).
Here's the order in which SwiftLint determines which Swift toolchain to use:
xcrun -find swift
sourcekitd.framework is expected to be found in the
usr/lib/ subdirectory of
the value passed in the paths above.
You may also set the
TOOLCHAINS environment variable to the reverse-DNS
notation that identifies a Swift toolchain version:
$ TOOLCHAINS=com.apple.dt.toolchain.Swift_2_3 swiftlint autocorrect
On Linux, SourceKit is expected to be located in
/usr/lib/libsourcekitdInProc.so or specified by the
Over 75 rules are included in SwiftLint and the Swift community (that's you!) continues to contribute more over time. Pull requests are encouraged.
See the Source/SwiftLintFramework/Rules directory to see the currently implemented rules.
opt_in_rules are disabled by default (i.e., you have to explicitly enable them
in your configuration file).
Guidelines on when to implement 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
Disable rules in code
Rules can be disabled with a comment inside a source file with the following format:
// swiftlint:disable <rule1> [<rule2> <rule3>...]
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>...]
// 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
It's also possible to modify a
enable command by appending
:next for only applying the command to the previous,
this (current) or next line respectively.
// 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
Configure SwiftLint by adding a
.swiftlint.yml file from the directory you'll
run SwiftLint from. The following parameters can be configured:
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
disabled_rules: # rule identifiers to exclude from running - colon - comma - control_statement opt_in_rules: # some rules are only opt-in - empty_count - missing_docs # 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 # 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 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)
Defining Custom Rules
You can define custom regex-based rules in you configuration file using the following syntax:
custom_rules: pirates_beat_ninjas: # rule identifier included: ".*.swift" # regex that defines paths to include during linting. optional. name: "Pirates Beat Ninjas" # rule name. optional. regex: "([n,N]inja)" # matching pattern 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
match_kinds, which will
reject matches that include syntax kinds that are not present in this list. Here
are all the possible syntax kinds:
SwiftLint supports nesting configuration files for more granular control over the linting process.
- Include additional
.swiftlint.ymlfiles 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.
includedare 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.
SwiftLint is maintained and funded by Realm Inc. The names and logos for Realm are trademarks of Realm Inc.