swift - 创建 Swift 闭包以创建 UIView

Question

我想将 DRY 应用于我在 swift 中创建的线条。我如何重构此代码以便调用闭包？它驻留在 View Controller 上。

var topLineView: UIView = {
    let lineView = UIView()
    lineView.layer.borderWidth = 1.0
    lineView.layer.borderColor = UIColor.lightGray.cgColor
    return lineView
}()

var bottomLineView: UIView = {
    let lineView = UIView()
    lineView.layer.borderWidth = 1.0
    lineView.layer.borderColor = UIColor.lightGray.cgColor
    return lineView
}()

var centerLineView: UIView = {
    let lineView = UIView()
    lineView.layer.borderWidth = 1.0
    lineView.layer.borderColor = UIColor.lightGray.cgColor
    return lineView
}()

我尝试创建一个变量但是导致了一个错误:

let lineView = {
    let lineView = UIView()
    lineView.layer.borderWidth = 1.0
    lineView.layer.borderColor = UIColor.lightGray.cgColor
    return lineView
}

var centerLineView = lineView()

错误(无法推断闭包类型等...)

Answer 1

Swift 无法推断闭包的返回类型，因此您需要提前告诉它您正在返回一个 UIView。这编译并运行良好。

let lineView = { () -> UIView in
    let lineView = UIView()
    lineView.layer.borderWidth = 1.0
    lineView.layer.borderColor = UIColor.lightGray.cgColor
    return lineView
}
var myViewFromClosure = lineView()
var myViewFromClosure2 = lineView()
var myViewFromClosure3 = lineView()

不过，在这种情况下，我个人会选择 function 而不是 closure。像这样:

func lineViewFunc() -> UIView {
    let lineView = UIView()
    lineView.layer.borderWidth = 1.0
    lineView.layer.borderColor = UIColor.lightGray.cgColor
    return lineView
}

var myViewFromFunc = lineViewFunc()
var myViewFromFunc2 = lineViewFunc()
var myViewFromFunc3 = lineViewFunc()