Xcode 5错误：表达式结果未使用

Question

So I am coding in Xcode 5 and I am working on a project that allows people to save an image that is displayed on the image view. I typed in this code...

[starImageView initWithImage:[UIImage imageNamed:@"star.jpg"]];

And then this error/warning came up...

"Expression result unused"

If you have ANY other questions about my project, let me know!

ALL answers are GREATLY appreciated!!!

Thanks!

Eric

Answer 1

According to Apple documentation , initWithImage is an instance method , which returns an UIImaveView object instance.

It does two things:

1: adjusts the reciever's frame (in your case starImageView) to match the size of the specified image

2: Returns another UIImageView initialized with the specified image.

Why you are getting the warning: You are not assigning the object returned by the method call. You should have something like this to get rid of this warning:

id newImageView = [starImageView initWithImage:[UIImage imageNamed:@"star.jpg"]];

(Then you will get a warning unused variable for newImageView, as you are assigning value but not using it anywhere)

Answer 2

如果starImageView已经初始化并且您尝试将图像设置为imageview，那么您应该使用以下语句。

[starImageView setImage:[UIImage imageNamed:@"star.jpg"]];