Question

我有一个图像裁剪功能，使用委托方法返回裁剪后的图像和CGRect。如何在另一个函数中的自定义完成块中返回它？

有没有办法引用该块，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

将稍后要调用的块类型的新属性（^(cropComplete)）添加到您的班级。

在cropImage:type:target:complete:内部功能将块保存到您的媒体资源中：

self.myNewBlockProperty = complete;

并在doneCropping:rect内调用该属性。

您无法访问＆＃39;完成＆＃39;其他函数中的参数但你可以将它保存在另一个变量/属性中，你可以毫无问题地访问它。

Answer 2

您可以在以后的实例变量中保存稍后要调用的块。

@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

从另一个函数使用完成块

2 个答案: