Blocks that create and return generic references and pointers to objects of any type. Demonstrates the use of id and const void * and CFBridgingRetain and CFBridgingRelease for generic programming purposes.

generics.m

// Returns a generic pointer to an object of any type
const void * (^object_t)(const unsigned long) = ^ const void * (const unsigned long index) {
    UIButton * button;
    [button = [UIButton new] setTag:index];
    printf("\nbutton == %p\n\n", &button);
    return (const id *)CFBridgingRetain(button);
};

// Outer block retains a generic pointer reference to an object of any type for subsequent calls to inner block
// Inner block returns the object referenced by the generic pointer retained by outer block
id _Nonnull (^(^ _Nonnull persistent_object_t)(const void * _Nonnull))(void) = ^ (const void * _Nonnull object_t) {
    return ^ id _Nonnull (void) {
        return (__bridge id _Nonnull)((__bridge const void * _Nonnull)CFBridgingRelease(object_t));
    };
};
typedef id _Nonnull (^object)(void); // Type definition for references to the inner block returned by the outer block (for delayed execution and storing as an element to a collection)

// Returns the object referenced by the generic pointer parameter
id _Nonnull (^ _Nonnull object_ref)(const void * _Nonnull) = ^ (const void * _Nonnull object_t) {
    printf("\nconst void * _Nonnull object_t == %p\n", object_t);
    return (__bridge id _Nonnull)((__bridge const void * _Nonnull)CFBridgingRelease(object_t));
};

// Invokes each block (except persistent_object_t)
static void(^generics)(void) = ^{
    const void * obj_t = object_t(1);    // a generic pointer to a UIButton object
    id _Nonnull obj = object_ref(obj_t); // a generic reference to the UIButton object pointed to by obj_t (cast to UIButton * prior to use)
    printf("\nobject_t == %p\n", obj_t); // 
    printf("\nobject == %p\n\n", &obj);
    
    object persistent_obj = persistent_object_t(obj_t); // retains the value of a generic pointer reference
    obj = persistent_obj(); 
};

/*

// Console output displaying the pointer value of a UIButton object and the value of the pointer to the object
// to validate object (and pointer reference) persistence between block invocations

button == 0x16db38868

const void * _Nonnull object_t == 0x102a0b9a0

object_t == 0x102a0b9a0

object == 0x16db38898