NSInvocationOperation initWithInvocation example ios

initWithInvocation:

Returns an NSInvocationOperation object initialized with the specified invocation object.

- (id)initWithInvocation:(NSInvocation *)inv

Parameters

inv

The invocation object identifying the target object, selector, and parameter objects.

Return Value( NSInvocationOperation initWithInvocation example )

An initialized NSInvocationOperation object or nil if the object could not be initialized.

Discussion

This method is the designated initializer. The receiver tells the invocation object to retain its arguments.

( NSInvocationOperation initWithInvocation example )

#import <Foundation/Foundation.h>

@interface Person : NSObject {
    NSString *name;
    NSUInteger age;
}
- (void)setName:(NSString *)personName age:(NSNumber *)personAge;
@end

@implementation Person
- (void)setName:(NSString *)personName age:(NSNumber *)personAge {
    NSLog(@"setName:%@ age:%@", personName, personAge);
    name = [personName copy];
    age = [personAge unsignedIntegerValue];
}
@end

int main() {
    NSAutoreleasePool *pool = [NSAutoreleasePool new];            
    Person *person = [Person new];

    SEL sel = @selector(setName:age:);

    NSMethodSignature *sig = [Person instanceMethodSignatureForSelector:sel];
    NSInvocation *inv = [NSInvocation invocationWithMethodSignature:sig];

    [inv setTarget:person];
    [inv setSelector:sel];

    NSString *name = nil;
    NSNumber *age = nil;

    [inv setArgument:&name atIndex:2];
    [inv setArgument:&age atIndex:3];

    // [inv retainArguments];
    // [inv invoke];

    NSInvocationOperation *op = [[[NSInvocationOperation alloc] initWithInvocation:inv] autorelease];
    NSOperationQueue *queue = [NSOperationQueue new];
    [queue addOperation:op];

    [pool release];
    return 0;
}

( NSInvocationOperation initWithInvocation example )

NSInvocationOperation *load = [[NSInvocationOperation alloc] initWithInvocation:loadInvoc];
NSAssert([loadInvoc argumentsRetained],@"Arguments have not been retained");
[loader release];

NSInvocation *completionInvoc = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:@selector(serviceCompletionBlock:afterInvocationCompleted:)]];
[completionInvoc setTarget:self];
[completionInvoc setSelector:@selector(serviceCompletionBlock:afterInvocationCompleted:)];

MFEImageCallback callback = [completionBlock copy];

[completionInvoc setArgument:&callback atIndex:2];
[completionInvoc setArgument:&load atIndex:3];

NSInvocationOperation *completion = [[NSInvocationOperation alloc] initWithInvocation:completionInvoc];
NSAssert([completionInvoc argumentsRetained],@"Completion handler not retaining");
[callback release];
[completion addDependency:load];

( NSInvocationOperation initWithInvocation example )

- (void)fetchImageWithURLs:(NSArray *)urlArray {
    [self.retriveAvatarQueue cancelAllOperations];
    self.retriveAvatarQueue = nil;

    NSOperationQueue *opQueue = [[NSOperationQueue alloc] init];

    for (NSUInteger i=0; i<[urlArray count]; i++) {
        NSURL *url = [urlArray objectAtIndex:i];

        NSInvocation *inv = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:@selector(cacheImageWithIndex:andURL:)]];
        [inv setTarget:self];
        [inv setSelector:@selector(cacheImageWithIndex:andURL:)];
        [inv setArgument:&i atIndex:2];
        [inv setArgument:&url atIndex:3];

        NSInvocationOperation *invOp = [[NSInvocationOperation alloc] initWithInvocation:inv];
        [opQueue addOperation:invOp];
        [invOp release];
    }

    self.retriveAvatarQueue = opQueue;
    [opQueue release];
}

- (void)cacheImageWithIndex:(NSUInteger)index andURL:(NSURL *)url {
    NSData *imageData = [NSData dataWithContentsOfURL:url];

    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSString *filePath = PATH_FOR_IMG_AT_INDEX(index);
    NSError *error = nil;

    // Save the file      
    if (![fileManager createFileAtPath:filePath contents:imageData attributes:nil]) {
        DLog(@"Error saving file at %@", filePath);
    }

    // Notifiy the main thread that our file is saved.
    [self performSelectorOnMainThread:@selector(imageLoadedAtPath:) withObject:filePath waitUntilDone:NO];

}