Objective-C: typedef'd a block, used it in a method declaration. How do I implement this?

Question

Just trying to get a handle on blocks. I get the concept. They're like function pointers, but they're actually objects; you can declare a block variable and assign it a block value; call it like a function; they get "frozen in time," for lack of a term, when they get executed, etc. I've created a few blocks and run them successfully, in a few different formats, but when it comes to using them in a method--either with a typedef or without--I'm having a lot of trouble. For example, here's an object interface I created, just to get a handle on the syntax. I have almost no idea how to implement it. ``` // AnObject.h #import <Foundation/Foundation.h> // The idea with the block and the method below is for the block to take // an int, multiply it by 3, and return a "tripled" int. The method // will then repeat: this process however many times the user wants via // the howManyTimes parameter and return that value in the form of an int. typedef int (^triple)(int); @interface AnObject : NSObjec…

Accepted Answer

Just call the block like a regular C function.

```
-(int)repeat:(int)howManyTimes withBlock:(triple)someBlock {
    for (int i = 0; i <= howManyTimes; i++) {
        int blockReturnValue = someBlock(i);
        // do something with blockReturnValue
    }
}
```

Update after your "further edit"

No, the block you passed in as an argument is run five times, each pass through the for loop.

- The first time, it invokes the block with `1` as the argument, and gets back `3`. It stores that in `blockReturnValue`, then goes on to the next iteration of the loop.

- The second time, it invokes the block with `2` as the argument, and gets back `6`. It stores that in `blockReturnValue`, completely overwriting the value we stored there in the previous pass.

- The third time, it inbokes the block with `3` as the argument, and gets back `9`. Again, it overwrites the value in `blockReturnValue`.

- The fourth time, we store `12` in `blockReturnValue`.

- The fifth time, we store `15` in `blockReturnValue`.

Then we exit the for loop, and return 15. So yes, you're correct that you've made a pointless method to multiply by 3. But you're doing it in a way that also does a bunch of useless calculations.

Objective-C: typedef'd a block, used it in a method declaration. How do I implement this?

Solution

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