iOS (ObjC) PromiseKit - Return promise within promise

Question

I'm trying to cascade a promise through some classes which add functionality at each level.

+ (AnyPromise *) method {
    return [SomeClass whichReturnsPromise]
    .then(^(id obj){
        // do stuff
        return obj;
    });
  }

Unfortunately this code is throwing an error on the second line:

exc_bad_access (code=1 address=0x10)

(Note: just calling return [SomeClass whichReturnsPromise] works fine)

I've scoured stackoverflow answers and tried many variations of the above code (which would work in javascript), but I keep getting the same error. How do I fix this?

score 2 · Accepted Answer · answered Jul 20 '16 at 00:19

2

Turns out a break case for [SomeClass which ReturnsPromise] was returning nil from before it was converted to return a promise. Changed it to return a promise with value nil. Works now.

answered Jul 20 '16 at 00:19

smileham

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gotnull · Answer 2 · 2016-07-19T23:24:57.130

0

Without testing, I think the following should work:

[self wait].then(^{
   return [SomeClass whichReturnsPromise];
}).then(^(id obj) {
   return obj;
});

I know the following is Swift, but if you have an AnyPromise you can use it in a Promise<T> chain:

someSwiftPromise().then { _ -> AnyPromise in
   // provided by `pod PromiseKit/SystemConfiguration`
   return SCNetworkReachability()
}.then { (obj: AnyObject?) in
   // AnyPromise always resolves with `AnyObject?`
}

edited Jul 19 '16 at 23:24

answered Jul 19 '16 at 23:18

gotnull

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What class is `[self wait]` from? I'm calling mine on a custom class. – smileham Jul 19 '16 at 23:20
Oh, then what happens if you add a semicolon `;` to your `return [SomeClass whichReturnsPromise]`. Do you get the same error? – gotnull Jul 19 '16 at 23:22
You mean if I take out the `.then` clause? No error. – smileham Jul 19 '16 at 23:24

iOS (ObjC) PromiseKit - Return promise within promise

2 Answers2