使用另一个函数的完成块

Question

我有一个带有委托方法的图像裁剪功能，returns 裁剪图像和 CGRect。我如何 return 在另一个函数中的自定义完成块中执行此操作？

有没有办法引用那个块，以便我可以在另一个函数中使用它？

很难解释，但这是我的代码：

- (void)cropImage:(UIImage *)image type:(NSInteger)type target:(id)target complete:(cropComplete)complete {
    CGFloat ratio;
    switch (type) {
        case 1:
            //16:9
            ratio = 16/9.0;
            break;
        case 2:
            //4:3
            ratio = 4/3.0;
            break;
        case 3:
            //1:1
            ratio = 1;
            break;

        default:
            break;
    }
    ImageCropViewController *vc = [ImageCropViewController new];
    vc.delegate = self;
    vc.imageToCrop = image;
    vc.ratio = ratio;
    UIViewController *targetVC = (UIViewController *)target;
    UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
    [targetVC presentViewController:nav animated:YES completion:nil];
}

//this is the delegate from ImageCropViewController above
- (void)doneCropping:(UIImage *)croppedImage rect:(CGRect)rect {
    (I want the image and CGRect here to return in the ^cropComplete block above)
}

Answer 1

向您的 class.

添加一个新的属性您稍后要调用的块类型 (^(cropComplete))

在 cropImage:type:target:complete: 函数中将块保存到您的属性:

self.myNewBlockProperty = complete;

并在 doneCropping:rect 内调用属性.

您无法在其他函数中访问 'complete' 参数，但您可以将其保存在另一个 variable/property 中，并且您可以毫无问题地访问它。

Answer 2

您可以简单地将稍后要调用的块保存在实例变量中。

@implementation WhateverClass
{
    cropComplete cropCompleteBlock;
}

- (void)cropImage:(UIImage *)image type:(NSInteger)type target:(id)target complete:(cropComplete)complete {
    cropCompletionBlock = complete;
    CGFloat ratio;
    switch (type) {
        case 1:
            //16:9
            ratio = 16/9.0;
            break;
        case 2:
            //4:3
            ratio = 4/3.0;
            break;
        case 3:
            //1:1
            ratio = 1;
            break;

        default:
            break;
    }
    ImageCropViewController *vc = [ImageCropViewController new];
    vc.delegate = self;
    vc.imageToCrop = image;
    vc.ratio = ratio;
    UIViewController *targetVC = (UIViewController *)target;
    UINavigationController *nav = [[UINavigationController alloc] initWithRootViewController:vc];
    [targetVC presentViewController:nav animated:YES completion:nil];
}

//this is the delegate from ImageCropViewController above
- (void)doneCropping:(UIImage *)croppedImage rect:(CGRect)rect {
    cropCompletionBlock(croppedImage);
    cropCompletionBlock = nil;
}

@end

使用另一个函数的完成块

use completion block from another function

protocols

block

objective-c

ios