#osx #ios #objective-c #blocks

block

Rust interface for Apple’s C language extension of blocks

9 releases

0.1.6 May 8, 2016
0.1.5 Apr 4, 2016
0.1.4 Nov 12, 2015
0.1.2 Oct 10, 2015
0.0.1 Apr 17, 2015

#4 in macOS APIs

Download history 900/week @ 2018-05-27 1013/week @ 2018-06-03 881/week @ 2018-06-10 997/week @ 2018-06-17 825/week @ 2018-06-24 947/week @ 2018-07-01 965/week @ 2018-07-08 1048/week @ 2018-07-15 1270/week @ 2018-07-22 1131/week @ 2018-07-29 1479/week @ 2018-08-05 1330/week @ 2018-08-12 1219/week @ 2018-08-19

3,124 downloads per month
Used in 249 crates (7 directly)

MIT license

16KB
290 lines

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

For more information on the specifics of the block implementation, see Clang's documentation: http://clang.llvm.org/docs/Block-ABI-Apple.html

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 {
    block.call((5, 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 { block.call((5, 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.

No runtime deps