Question

我正在尝试将ObjC代码翻译成swift版本。我在'Block'和'Closure'之间有一些混淆点。

正如图片所示，有一个“完成：^（...）”，这使我无法解决它。
“if（中途）中途（完成）”和“if（完成）完成（完成）”是什么意思？为什么存在“;”在控制流程之后？

非常感谢您的帮助和指导。

Ethan Joe

ObjC版本：

- (void)flipTransitionWithOptions:(UIViewAnimationOptions)options halfway:(void (^)(BOOL finished))halfway completion:(void (^)(BOOL finished))completion
{
    CGFloat degree = (options & UIViewAnimationOptionTransitionFlipFromRight) ? -M_PI_2 : M_PI_2;

CGFloat duration = 0.4;
CGFloat distanceZ = 2000;
CGFloat translationZ = self.frame.size.width / 2;
CGFloat scaleXY = (distanceZ - translationZ) / distanceZ;

CATransform3D rotationAndPerspectiveTransform = CATransform3DIdentity;
rotationAndPerspectiveTransform.m34 = 1.0 / -distanceZ; // perspective
rotationAndPerspectiveTransform = CATransform3DTranslate(rotationAndPerspectiveTransform, 0, 0, translationZ);

rotationAndPerspectiveTransform = CATransform3DScale(rotationAndPerspectiveTransform, scaleXY, scaleXY, 1.0);
self.layer.transform = rotationAndPerspectiveTransform;

[UIView animateWithDuration:duration / 2 animations:^{
    self.layer.transform = CATransform3DRotate(rotationAndPerspectiveTransform, degree, 0.0f, 1.0f, 0.0f);
} completion:^(BOOL finished){
    if (halfway) halfway(finished);
    self.layer.transform = CATransform3DRotate(rotationAndPerspectiveTransform, -degree, 0.0f, 1.0f, 0.0f);
    [UIView animateWithDuration:duration / 2 animations:^{
        self.layer.transform = rotationAndPerspectiveTransform;
    } completion:^(BOOL finished){
        self.layer.transform = CATransform3DIdentity;
        if (completion) completion(finished);
    }];
}];






My Swift Version:
    func flipTransitionWithOptions(var options:UIViewAnimationOptions, _halfway halfway:((finished: Bool) -> Void)?, _completion completion:((finished: Bool) -> Void)?) {
        var degree: CGFloat!
        if(options == UIViewAnimationOptions.TransitionFlipFromRight){
            degree = CGFloat(-M_PI_2)
        } else {
            degree = CGFloat(M_PI_2)
        }
        var duration: CGFloat = 0.4
        var distanceZ: CGFloat = 2000
        var translationZ: CGFloat = self.frame.width / 2
        var scaleXY: CGFloat = (distanceZ - translationZ) / distanceZ

    var rotationAndPerspectiveTrabsform: CATransform3D = CATransform3DIdentity
    rotationAndPerspectiveTrabsform.m34 = 1.0 / (-distanceZ)
    rotationAndPerspectiveTrabsform = CATransform3DTranslate(rotationAndPerspectiveTrabsform, 0, 0, translationZ)
    rotationAndPerspectiveTrabsform = CATransform3DScale(rotationAndPerspectiveTrabsform, scaleXY, scaleXY, 1.0)
    layer.transform = rotationAndPerspectiveTrabsform

    UIView.animateWithDuration(0.2, animations: {self.layer.transform = CATransform3DRotate(rotationAndPerspectiveTrabsform, degree, 0.0, 1.0, 0.0)}, completion: {finished in
    self.layer.transform = CATransform3DRotate(rotationAndPerspectiveTrabsform, -degree, 0.0, 1.0, 0.0)
        UIView.animateWithDuration(0.2, animations: {self.layer.transform = rotationAndPerspectiveTrabsform}, completion: {finished in self.layer.transform = CATransform3DIdentity})
    })

}

Answer 1

在您未使用finished参数的任何情况下，将参数名称_替换为finished。在Objective C版本中，finished被传递给您从Swift转换中省略的附加函数处理程序。

swift中的

_表示参数未使用。在Swift文档中，它向您显示如果未使用，可以省略闭包中的许多项，因此请务必学习Swift语言指南以了解这些细微差别和选项。

^ {}格式只是ObjC，在Swift中不需要。只是{}

看起来开发人员添加了行，可选择分别调用补充完成处理函数（如果存在）...分别调用halfway和completion。它们几乎肯定是函数指针，但completion可能不是最佳选择，因为它恰好与函数参数同名。

您应该检查原始代码，看看源代码中是否有名为halfway或completion的函数或闭包，以确保您没有遗漏一些也需要的基本代码完成运行时调用。

翻译（Block：Objective-C）到（Closure：Swift）请验证我的代码

1 个答案: