swift - --> (dash dash greater than) 运算符在 Swift 中是什么意思

Question

我看GPUImage2的源码

    picture = PictureInput(image:UIImage(named:"WID-small.jpg")!)
    filter = SaturationAdjustment()
    picture --> filter --> renderView
    picture.processImage()

--> 是做什么的？

Answer 1

这是一个声明为将目标添加到源的运算符。

infix operator --> : AdditionPrecedence
//precedencegroup ProcessingOperationPrecedence {
//    associativity: left
////    higherThan: Multiplicative
//}
@discardableResult public func --><T:ImageConsumer>(source:ImageSource, destination:T) -> T {
    source.addTarget(destination)
    return destination
}

函数在pipeline.swift文件中声明

addTarget 函数也非常 self 描述。

public func addTarget(_ target:ImageConsumer, atTargetIndex:UInt? = nil) {
    if let targetIndex = atTargetIndex {
        target.setSource(self, atIndex:targetIndex)
        targets.append(target, indexAtTarget:targetIndex)
        transmitPreviousImage(to:target, atIndex:targetIndex)
    } else if let indexAtTarget = target.addSource(self) {
        targets.append(target, indexAtTarget:indexAtTarget)
        transmitPreviousImage(to:target, atIndex:indexAtTarget)
    } else {
        debugPrint("Warning: tried to add target beyond target's input capacity")
    }
}

编辑 正如其他人所说，运算符(operator)是该项目的自定义运算符(operator)，截至 2018 年 3 月 29 日，该运算符(operator)并未内置在 swift 语言中