CODEWITHSUNDEEP
iphoneobjective-ccocoa-touch
fuzzygoat
fuzzygoat

Reputation: 26223

Property "window" not found on object?

This came up in another question (kindly answered by meronix) but I curious to learn a little more about what is going on here, is this a LLVM/Clang issue, or are the two statements different in someway.

enter image description here

I know I can fix this by adding (See below), so more curious than anything ...

enter image description here

Upvotes: 0

Views: 792

Answers (1)

Jonathan Grynspan
Jonathan Grynspan

Reputation: 43472

The two statements are different. A property can only be used if the type of the lvalue declares the property. This is because the getter and setter for the property might be non-obvious (often the case with boolean properties, where the getter is explicitly set to isSomething.) The compiler cannot infer that without strong type info.

The [lvalue message] syntax, however, has no such ambiguity, so the compiler allows it. Since the type of the lvalue is id, any known message can be sent to it without a compiler warning. The compiler will only warn if two signatures correspond to the same selector (for instance, one class has - (UIWindow *)window and another has - (int)window.)

The UIApplicationDelegate protocol defines a window property, so when you explicitly type your object as id <UIApplicationDelegate>, the compiler knows about the property and can use it.

Upvotes: 6

Related Questions