Month: June 2021

Why do you need SwiftLint?

1. It speed ups code reviews, you stop wasting time on code formatting, force casting, and other common issues
2. It improves the code quality, code becomes more readable, and maintainable

Integration

1. Add SwiftLint to a podfile

Or use another option from the official documentation.

  # A tool to enforce Swift style and conventions.
  pod 'SwiftLint', '0.43.1'

2. Add this .swiftlint.yml config file to the project root folder

The main trick to make integration easy is to disable all rules at first.

disabled_rules:
- trailing_whitespace
- force_cast
- force_unwrapping
- force_try
- empty_string
- line_length
- mark
- weak_delegate
- unneeded_break_in_switch
- identifier_name
- function_parameter_count
- unused_closure_parameter
- vertical_whitespace
- opening_brace
- control_statement
- statement_position
- comma
- colon
- trailing_comma

opt_in_rules:
- empty_count
- empty_string

excluded:
- Carthage
- Pods
- SwiftLint/Common/3rdPartyLib

line_length:
    warning: 150
    error: 200
    ignores_function_declarations: true
    ignores_comments: true
    ignores_urls: true

function_body_length:
    warning: 300
    error: 500

function_parameter_count:
    warning: 6
    error: 8

type_body_length:
    warning: 300
    error: 500

file_length:
    warning: 1000
    error: 1500
    ignore_comment_only_lines: true

cyclomatic_complexity:
    warning: 15
    error: 25

reporter: "xcode"

3. Build a project, add additional rules to the disabled_rules section, if there are many warnings for them

4. Delete rules from the disabled_rules section one by one and fix all the warnings

5. Leave the trailing_whitespace and other rules that you don’t want to fix in the disabled_rules section

In the end, you will have something like this in your config file.

disabled_rules:
- trailing_whitespace

opt_in_rules:
- empty_count
- empty_string

excluded:
- Carthage
- Pods
- SwiftLint/Common/3rdPartyLib

line_length:
    warning: 150
    error: 200
    ignores_function_declarations: true
    ignores_comments: true
    ignores_urls: true

function_body_length:
    warning: 300
    error: 500

function_parameter_count:
    warning: 6
    error: 8

type_body_length:
    warning: 300
    error: 500

file_length:
    warning: 1000
    error: 1500
    ignore_comment_only_lines: true

cyclomatic_complexity:
    warning: 15
    error: 25

reporter: "xcode"

Some ideas on how to fix common code issues

Force Cast Violation: Force casts should be avoided. (force_cast)

Problem:

let cell = collectionView.dequeueReusableCell(
    withReuseIdentifier: "DocumentCollectionViewCell",
    for: indexPath
) as! DocumentCollectionViewCell

Solution:

guard let cell = collectionView.dequeueReusableCell(
    withReuseIdentifier: "DocumentCollectionViewCell",
    for: indexPath
) as? DocumentCollectionViewCell else { fatalError() }

Force Try Violation: Force tries should be avoided. (force_try)

Problem:

let workingDirectory = try! FileManager.default.url(
    for: .documentDirectory,
    in: .userDomainMask,
    appropriateFor: nil,
    create: false
)

Solution:

do {
    let workingDirectory = try FileManager.default.url(
        for: .documentDirectory,
        in: .userDomainMask,
        appropriateFor: nil,
        create: false
    )
} catch {
    print(error)
}

Exceptions

In very rare cases you will not be able to fix the warning. For example, when you use a framework and you cannot easily change its API. Then you can switch off a SwiftLint rule for a particular code block using // swiftlint:disable rule_name and // swiftlint:enable rule_name comments.