Why do you need SwiftLint?
- It speed ups code reviews, you stop wasting time on code formatting, force casting, and other common issues
- 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.
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# 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.
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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.
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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:
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let cell = collectionView.dequeueReusableCell( withReuseIdentifier: "DocumentCollectionViewCell", for: indexPath ) as! DocumentCollectionViewCell |
Solution:
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guard let cell = collectionView.dequeueReusableCell( withReuseIdentifier: "DocumentCollectionViewCell", for: indexPath ) as? DocumentCollectionViewCell else { fatalError() } |
Force Try Violation: Force tries should be avoided. (force_try)
Problem:
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let workingDirectory = try! FileManager.default.url( for: .documentDirectory, in: .userDomainMask, appropriateFor: nil, create: false ) |
Solution:
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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.