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I have to provide a C-style callback for a specific C library in an iOS app. The callback has no void *userData or something similar. So I am not able to loop in a context. I'd like to avoid introducing a global context to solve this. An ideal solution would be an Objective-C block.
My question: Is there a way to 'cast' a block into a function pointer or to wrap/cloak it somehow?
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Objective-C programming language allows you to pass a pointer to a function. To do so, simply declare the function parameter as a pointer type. Following a simple example where we pass an unsigned long pointer to a function and change the value inside the function which reflects back in the calling function −.
A block declaration follows the next syntax pattern: This is quite similar to a C function declaration, with one great exception: The caret (^) symbol, which indicates that the declared object is a block. Let’s see everything one by one: ReturnType: Any data type Objective-C supports, or void if the block returns nothing.
Like any variable or constant, you must declare a pointer before you can use it to store any variable address. The general form of a pointer variable declaration is −. type *var-name; Here, type is the pointer's base type; it must be a valid Objective-C data type and var-name is the name of the pointer variable.
Objective-C allows you to have pointer on a pointer and so on. Passing an argument by reference or by address both enable the passed argument to be changed in the calling function by the called function. Objective-C allows a function to return a pointer to local variable, static variable and dynamically allocated memory as well.
MABlockClosure can do exactly this. But it may be overkill for whatever you need.
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