Rust interface for Apple's C language extension of blocks.
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.

Rust interface for Apple's C language extension of blocks.

For more information on the specifics of the block implementation, see Clang's documentation:

Invoking blocks

The Block struct is used for invoking blocks from Objective-C. For example, consider this Objective-C function:

int32_t sum(int32_t (^block)(int32_t, int32_t)) {
    return block(5, 8);

We could write it in Rust as the following:

unsafe fn sum(block: &Block<(i32, i32), i32>) -> i32 {, 8))

Note the extra parentheses in the call method, since the arguments must be passed as a tuple.

Creating blocks

Creating a block to pass to Objective-C can be done with the ConcreteBlock struct. For example, to create a block that adds two i32s, we could write:

let block = ConcreteBlock::new(|a: i32, b: i32| a + b);
let block = block.copy();
assert!(unsafe {, 8)) } == 13);

It is important to copy your block to the heap (with the copy method) before passing it to Objective-C; this is because our ConcreteBlock is only meant to be copied once, and we can enforce this in Rust, but if Objective-C code were to copy it twice we could have a double free.