Unused Closure Parameter

Unused parameter in a closure should be replaced with _

• Identifier: unused_closure_parameter
• Enabled by default: Yes
• Supports autocorrection: Yes
• Kind: lint
• Analyzer rule: No
• Minimum Swift compiler version: 5.0.0
• Default configuration:

  Key	Value
  severity	warning

Non Triggering Examples

[1, 2].map { $0 + 1 }

[1, 2].map({ $0 + 1 })

[1, 2].map { number in
 number + 1 
}

[1, 2].map { _ in
 3 
}

[1, 2].something { number, idx in
 return number * idx
}

let isEmpty = [1, 2].isEmpty()

violations.sorted(by: { lhs, rhs in 
 return lhs.location > rhs.location
})

rlmConfiguration.migrationBlock.map { rlmMigration in
    return { migration, schemaVersion in
        rlmMigration(migration.rlmMigration, schemaVersion)
    }
}

genericsFunc { (a: Type, b) in
    a + b
}

var label: UILabel = { (lbl: UILabel) -> UILabel in
    lbl.backgroundColor = .red
    return lbl
}(UILabel())

hoge(arg: num) { num in
    return num
}

({ (manager: FileManager) in
  print(manager)
})(FileManager.default)

withPostSideEffect { input in
    if true { print("\(input)") }
}

viewModel?.profileImage.didSet(weak: self) { (self, profileImage) in
    self.profileImageView.image = profileImage
}

let failure: Failure = { task, error in
    observer.sendFailed(error, task)
}

List($names) { $name in
    Text(name)
}

List($names) { $name in
    TextField($name)
}

_ = ["a"].filter { `class` in `class`.hasPrefix("a") }

let closure: (Int) -> Void = { `foo` in _ = foo }

let closure: (Int) -> Void = { foo in _ = `foo` }

Triggering Examples

[1, 2].map { ↓number in
 return 3 }

[1, 2].map { ↓number in
 return numberWithSuffix }

[1, 2].map { ↓number in
 return 3 // number }

[1, 2].map { ↓number in
 return 3 "number" }

[1, 2].something { number, ↓idx in
 return number }

genericsFunc { (↓number: TypeA, idx: TypeB) in return idx }

let c: (Int) -> Void = { foo in _ = .foo }

hoge(arg: num) { ↓num in
}

fooFunc { ↓아 in }

func foo () {
 bar { ↓number in return 3 }

viewModel?.profileImage.didSet(weak: self) { (↓self, profileImage) in
    profileImageView.image = profileImage
}

let failure: Failure = { ↓task, error in
    observer.sendFailed(error)
}

List($names) { ↓$name in
    Text("Foo")
}

let class1 = "a"
_ = ["a"].filter { ↓`class` in `class1`.hasPrefix("a") }