Expand description
A Rust interface for Objective-C 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 i32
s, 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.
Structs
- An Objective-C block that takes arguments of
A
when called and returns a value ofR
. - An Objective-C block whose size is known at compile time and may be constructed on the stack.
- A reference-counted Objective-C block.
Traits
- Types that may be used as the arguments to an Objective-C block.
- Types that may be converted into a
ConcreteBlock
.