到 NSIndexPath 的隐式转换错误

Question

>我有这个相对简单的辅助方法：

- (float)imageHeightForRowAtIndexPath:(NSIndexPath *)indexPath
{
    CGRect screenRect = [[UIScreen mainScreen] bounds];
    CGFloat screenWidth = screenRect.size.width;
    float imageWidth = [[self.widthArray objectAtIndex:indexPath.row] floatValue];
    float ratio = screenWidth/imageWidth;
    float imageHeight = ratio * [[self.heightArray objectAtIndex:indexPath.row] floatValue];
    return imageHeight;
}

在另一个方法中调用时，它在此方法中完全正常工作：

- (UIImage *)imageWithImage:(UIImage *)image forRowAtIndexPath:(NSIndexPath *)indexPath
{
    CGRect screenRect = [[UIScreen mainScreen] bounds];
    CGFloat newWidth = screenRect.size.width;
    CGFloat newHeight = [self imageHeightForRowAtIndexPath:indexPath.row];
    UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight ));
    [image drawInRect:CGRectMake(0, 0, newWidth, newHeight)];
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return newImage;
}

编译器说： Implicit conversion from 'NSInteger' to 'NSIndexPath' is disallowed

我不知道为什么以及如何解决这个问题。知道吗？

Answer 1

您有 2 种方法：

1. - (float)imageHeightForRowAtIndexPath:(NSIndexPath *)indexPath
2. - (UIImage *)imageWithImage:(UIImage *)image forRowAtIndexPath:(NSIndexPath *)indexPath

每个参数都有一个NSIndexPath *参数。

现在，在imageWithImage:forRowAtIndexPath:中，您正在呼叫imageHeightForRowAtIndexPath:：

[self imageHeightForRowAtIndexPath:indexPath.row]

在那条线上，您正在从indexPath（NSInteger）中获取row并尝试将其传递给imageHeightForRowAtIndexPath:：，这期待NSIndexPath *.

这是导致错误的原因，因为编译器知道期望NSIndexPath *并且知道您正在提供NSInteger。

若要解决，请将代码更改为：

CGFloat newHeight = [self imageHeightForRowAtIndexPath:indexPath];