Question

It must be one of those things where there’s a tiny mistake i’ve missed, or something, but i can’t seem to figure it out.

Viewcontroller.h

#import "RGBEditView.h"
@interface ColorPickerView : UIViewController {
RGBEditView *rgbEditView;
}
-(void)showRGBEditor;

.m

-(void)showRGBEditor {
rgbEditView = [[RGBEditView alloc] initWithFrame:CGRectMake(0, 0, 280, 46) H:h S:s B:b];
}

It’s this line above, the initwithframe line, that gives the error 'Incompatible Objective-C types assigning '*', expected '*'

RGBEditView.h

@interface RGBEditView : UIView {
}
-(RGBEditView *)initWithFrame:(CGRect)frame H:(float)hue S:(float)saturation B:(float)brightness;

RGBEditView.m

-(RGBEditView *)initWithFrame:(CGRect)frame H:(float)hue S:(float)saturation B:(float)brightness {
[super initWithFrame:frame];
 return self;
}

Can anybody see my problem? I’m very confused about this.

EDIT:

The problem lies in that I have another class which also uses initWithFrame:H:S:B:, so the only way to fix this is to change on of them to something a bit different, but this seems like an awkward work around. Any other solutions?

Answer 1

the methods init and methods that start with initWith should return type id.

what typically happens is that you have 2 classes with the same method name (initializer in this case), but differ in their return types:

RGBEditView

  -(RGBEditView *)initWithFrame:(CGRect)frame H:(float)h S:(float)s B:(float)b;

HSBEditView

  -(HSBEditView *)initWithFrame:(CGRect)frame H:(float)h S:(float)s B:(float)b;

alloc returns id – the compiler warns you because it sees an expression which resembles type assignment used in the following example:

RGBEditView * rgb = /* ... */;
HSBEditView * hsb = nil;
hsb = rgb // << compiler: "hey - you don't want to do that unless
          //               RGBEditView were a subclass of
          //               HSBEditView... but it's not!"

you correct this by returning id from your initializers, like this:

-(id)initWithFrame:(CGRect)frame H:(float)h S:(float)s B:(float)b;

you return id to avoid clashes like this, and because the compiler doesn’t know what type is returned via alloc, so every subclass declaration would have to return a different type – which would only lead to more problems.

the exception to this is to use well qualified names – and is typically seen in convenience constructors:

+ (HSBEditView *)newHSBEditViewWithFrame:(CGRect)frame
                                       H:(float)h S:(float)s B:(float)b;