Setting more than one argument for NSInvocationOperation

Question

-[NSInvocationOperation initWithTarget:selector:object:] only accepts one object to be passed as an argument for the method that will be called. I want to use two arguments; how can I do that?

This is my code:

- (void)loadImage:(NSURL *)imageURL
{
    NSOperationQueue *queue = [NSOperationQueue new];
    NSInvocationOperation *operation = [[NSInvocationOperation alloc]
                                        initWithTarget:self
                                        selector:@selector(requestRemoteImage:)
                                        object:imageURL];
    [queue addOperation:operation];
}

- (void)requestRemoteImage:(NSURL *)imageURL
{
    NSData *imageData = [[NSData alloc] initWithContentsOfURL:imageURL];
    UIImage *image = [[UIImage alloc] initWithData:imageData];

    [self performSelectorOnMainThread:@selector(placeImageInUI:) withObject:image waitUntilDone:YES];
}

@H2CO3's answer is exactly correct, but I would strongly discourage using `NSInvocationOperation` unless you have a strong need for it. `NSBlockOperation` is much faster to generate, easier to code, and more flexible. Invocations are extremely expensive to create, and have been widely replaced with blocks. — Rob Napier, Aug 28 '12 at 17:28

score 1 · Answer 1 · answered Aug 28 '12 at 17:26

You can either use an NSInvocation object to initialize the opertation:

- (id)initWithInvocation:(NSInvocation *)inv

(NSInvocation can handle multiple arguments); or you can wrap the needed arguments to an NSArray or NSDictionary, provided they're objects.

score 1 · Answer 2 · edited May 23 '17 at 11:49

1

Ask the operation for its invocation and modify that before adding the operation to the queue.

 NSInvocation * invocation = [operation invocation];
 [invocation setArgument:&anotherObject atIndex:3];    
 // Indexes 0 and 1 are self and cmd, and you've already used index 2

Or, as Rob Napier suggested, use NSBlockOperation, which is far more flexible and easy to use.

edited May 23 '17 at 11:49

Community

1
1

answered Aug 28 '12 at 17:39

jscs

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i want to use the new argument in requestRemoteImage method – Khalid Aug 28 '12 at 18:35

score -1 · Accepted Answer · answered Aug 28 '12 at 17:25

-1

you could send a dictionary with all the values you want

answered Aug 28 '12 at 17:25

Ismael

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Develop your answer a little, above all when it's for a new user who may not be as experimented as you – Jaffa Aug 29 '12 at 07:20
@Geoffroy You're right . but I try to apply it and succeeded . – Khalid Aug 29 '12 at 08:55
@besharkhalid no problem, I was just reviewing new answers :) – Jaffa Aug 29 '12 at 09:30

Setting more than one argument for NSInvocationOperation

3 Answers3