warning: initialization from distinct Objective-c type (iPhone Development)
This warning is raised by Xcode whenever an implicit or INCORRECT type cast is occurring.
(The AS3 equivilant is the error: Error # 1067: Implicit coercion of a value of type * to an unrelated type *.)
"Distinct Objective-C type" is the type id. Apple docs say, "In Objective-C, object identifiers are a distinct data type: id. This type is defined as a pointer to an object..."
Example Causes:
NSMutableArray* myArraySorted = [myArray sortedArrayUsingSelector:@selector(compare:)];
The above will raise "warning: initialization from distinct Objective-c type" because sortedArrayUsingSelector returns an object of type id. We can correct this by simply casting the return value to the type NSMutableArray* as follows.
NSMutableArray* myArraySorted = (NSMutableArray*)[myArray sortedArrayUsingSelector:@selector(compare:)];
Finally notice that the incorrect cast that follows will also raise this warning:
NSMutableArray* myArraySorted = (NSString*)[myArray sortedArrayUsingSelector:@selector(compare:)];
Hence, whenever you see: "warning: initialization from distinct Objective-c type" you are performing an implicit cast.
(The AS3 equivilant is the error: Error # 1067: Implicit coercion of a value of type * to an unrelated type *.)
"Distinct Objective-C type" is the type id. Apple docs say, "In Objective-C, object identifiers are a distinct data type: id. This type is defined as a pointer to an object..."
Example Causes:
NSMutableArray* myArraySorted = [myArray sortedArrayUsingSelector:@selector(compare:)];
The above will raise "warning: initialization from distinct Objective-c type" because sortedArrayUsingSelector returns an object of type id. We can correct this by simply casting the return value to the type NSMutableArray* as follows.
NSMutableArray* myArraySorted = (NSMutableArray*)[myArray sortedArrayUsingSelector:@selector(compare:)];
Finally notice that the incorrect cast that follows will also raise this warning:
NSMutableArray* myArraySorted = (NSString*)[myArray sortedArrayUsingSelector:@selector(compare:)];
Hence, whenever you see: "warning: initialization from distinct Objective-c type" you are performing an implicit cast.
Labels: iPhone Cocoa UIKit Objective-C
posted by Andrew Paul Simmons at
9:05 PM
1 Comments:
Thanks, you've just saved a lot of my time :)
Thanks for the post. I get what you're trying to say but I must be slow because I don't know how to fix the warning in the project I'm working on. I downloaded this sample project from icodeblog.com.
I haven't changed anything, so you should be able to open up the project and take a look. What do I need to change in the project?
this helped ! thanks :) i kept on getting it from writing
MKPinAnnotationView *view = [mView dequeueReusableAnnotationViewWithIdentifier:@"PIN_ANNOTATION"];
then thanks to you..i changed to
MKPinAnnotationView *view = (MKPinAnnotationView *)[mView dequeueReusableAnnotationViewWithIdentifier:@"PIN_ANNOTATION"];
thanks . it solved my problem.
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