如何将 UIImage 添加到 Objective-C 中的 MSMutableArray？

Question

I have noob objective-c question. How do you add an UIImage to a MSMutableArray? Here is the code that I have:

MSMutableArray *arr = [[NSMutableArray alloc] init];
UIImage *image;
UIGraphicsBeginImageContext(contextSize);
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(context, 0, pushUpSize);

    [screenWindow.layer renderInContext: context];  
    image = UIGraphicsGetImageFromCurrentImageContext();
}
UIGraphicsEndImageContext();
[arr addObject:image];

But this crashes the program when it tries to add the image. I read somewhere that its adding a variable but not the pointer, is that correct? How do I add the UIImage to the array, its an object isn't it?

Thanks!

Answer 1

You are initializing the array arr but adding the images to the (apparently unitialized) array imageArr .

Based on your updated code, I would say that the image object is probably nil . Calling addObject: with a nil value is specifically prohibited in the docs .

Answer 2

@thiesdiggity: Not much is wrong in your code from what I can see. But just try out the below code as I think the image object is nil :

MSMutableArray *arr = [[NSMutableArray alloc] init];
UIImage *image;
UIGraphicsBeginImageContext(contextSize);
{
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(context, 0, pushUpSize);

    [screenWindow.layer renderInContext: context];  
    image = UIGraphicsGetImageFromCurrentImageContext();
}
UIGraphicsEndImageContext();

if(image != nil)
{
    [arr addObject:image];
}

Let me know if you need more help and please post your crash log for more help

Hope this helps.