为什么我不能调用此方法？

Question

I have a method signature here:

.h

-(void)addToArray

And I want to use it here:

.m 

-(void)viewDidLoad{
NSMutableArray *array = [[NSMutableArray alloc]init];
[array addToArray];
}

-(void)addToArray{
//some code here…
}

The problem is that when I do [array addToArray]; it returns to me a message that says "Instance method '-addToArray' not found (return type defaults to 'id')" How can I solve it?

Answer 1

when you do [array somemethod] ..it will look for the method in that array data type class( that is in NSMutableArray class.

when you have a method in your own class.and it is not a category...then you must call

[self somemethod]

this way it will look in the class that is in which you are calling the method.

Answer 2

Change to:

.h

-(void)addObjectsToArray:(NSMutableArray*)a;

.m

- (void)viewDidLoad {
     NSMutableArray * array = [[NSMutableArray alloc]init];
     [self addObjectsToArray:array];
}
- (void)addObjectsToArray:(NSMutableArray*)a {
     //some code here…
     [a addObject:[NSString stringWithFormat:@"Example String Object"]]; // example way to add objects to the array
}

Answer 3

Shubhank's answer is indeed correct, however if you want to accomplish what you'd initially described, that is have the have the NSMutableArray instance respond to your method, you can achieve that through the use of categories. https://developer.apple.com/library/ios/#documentation/cocoa/conceptual/objectivec/chapters/occategories.html

This blog details adding a category to NSArray and/or NSMutableArray. http://it.toolbox.com/blogs/macsploitation/extending-classes-in-objectivec-with-categories-27447

Answer 4

In your m file, try doing this: #import "whatever its called.h" if you haven't yet. If you provide more code I can give more help, but I hope this helps.