Multiple methods named “count” found with mismatch

问题:

Since the update to Xcode 5.1 I can't archive my project any more. Xcode always says "Multiple methods named "count" found with mismatched result, parameter type or attributes. This problem is new and simulator and running on device works fine. Here is the code:

    for ( int i = 0; i<[parseJSONArray count];i++){
        for (int j = 0; j<[JSON[@"data"][@"menu"][i][@"item"] count];j++){
            [pictureURL addObject:JSON[@"data"][@"menu"][i][@"item"][j][@"image"]];
        }
    }

Xcode shows the error at this point : [JSON[@"data"][@"menu"][i][@"item"] count] JSON is a NSDictionary. Whats wrong with this?

回答1:

Ask yourself: What is the type of JSON[@"data"][@"menu"][i][@"item"] ? It is "id". The compiler doesn't know which method this object responds to. You send a "count" message. The compiler goes through all the count methods of all classes that it knows about. If there are more than two different ones, it has to complain.

You could write

NSDictionary* data = JSON [@"data"];
NSArray* menu = data [@"menu"];
NSDictionary* menuI = menu [i];
NSArray* item = menuI [@"item"];

for (NSDictionary* picture in item)
    [pictureURL addObject:picture [@"image"];

More readable, easier to follow, runs faster, and easier to debug.

Of course you can also write

for (NSUInteger j = 0; j < item.count; ++j)
{
    NSDictionary* picture = item [i];
    [pictureURL addObject:picture [@"image"];
}

回答2:

Since there are multiple Cocoa classes with a method named count, and objectForKeyedSubscript: (to which JSON[@"data"][@"menu"][i][@"item"] resolves) returns id, the compiler can't do the typechecking it wants to do for the message send.

To stop the warning, you'll need to cast the result of JSON[@"data"][@"menu"][i][@"item"] to its actual class e.g., (NSDictionary *)(JSON[@"data"][@"menu"][i][@"item"]), or put it into a temporary variable: NSDictionary * itemDict = JSON[@"data"][@"menu"][i][@"item"];

回答3:

Try:

[[[[[JSON objectForKey:@"data"] objectForKey:@"menu"] objectAtIndex: i] objectForKey:@"item"] count];

That help?

回答4:

Just a cast like:

float a = [[_myArray objectForKey:@"myKey"] count] / 5.0;

float a = [(NSArray *)[_myArray objectForKey:@"myKey"] count] / 5.0;

回答5:

try with like this

for ( int i = 0; i<[(NSArray *)parseJSONArray count];i++){
    for (int j = 0; j<[JSON[@"data"][@"menu"][i][@"item"] count];j++){
        [pictureURL addObject:JSON[@"data"][@"menu"][i][@"item"][j][@"image"]];
    }
}

you need to passing

parseJSONArray

type of NSArray

回答6:

In case you don't want to write code like this [((NSArray*)aId) count]:

@interface NSArray ()
- (NSUInteger) arrayElementCount;
@end

@implementation NSArray()
- (NSUInteger) arrayElementCount {
    return [self count];
}
@end

Using arrayElementCount instead of 'count'