"Convenience initializer missing a 'self' call to another initializer"

Question

I'm trying convert my code to iOS 8 project, and i need some explanation on how to fix this warning: "Convenience initializer missing a 'self' call to another initializer"

on this code:

-(instancetype) initWithCoder:(NSCoder *)aDecoder // warning: Convenience initializer missing a 'self ' call to another initializer
{
    if (self = [super initWithCoder:aDecoder]) // warning: convenience initializer should not invoke an initializer on 'super'
    {
    // some init stuff here
    }
    return self;
}

Answer 1

The new Clang shipping with Xcode 6 enables compiler-enforced designated initializers through the NS_DESIGNATED_INITIALIZER macro. When it marks any one of the init-family methods in a class's declaration, all other initializers are considered "secondary" (to use Apple's terminology) initializers. That is, they should call through to one another designated or secondary initializer until they reach a designated initializer.

UIView marks nothing as the designated initializer, so somewhere you've declared another init method of the class as the designated initializer. Because of that, NSCoder's initializer becomes marked as secondary and generates a warning. I've filed a radar (rdar://17559176) about it, but until then it can be turned off on a per-file basis by specifying -Wno-objc-designated-initializers, or by providing the appropriate diagnostic push-pop with -Wobjc-designated-initializers.

Answer 2

Just an addendum to what @CodaFi is saying:

• One slice of Apple docs I found on designated initializers is here.
• I've answered a question on how to suppress these warnings here, with a couple more options. I particularly like the precompiled header method (#2), because it reminds you to fix it.