Type cast array elements in for loop

Question

In a delegate method, I get back a ‘results’ array of a custom object type, and I want to loop through the array elements. I do the following now, and this works

for result in results {
    if result is XYZClass {     
        //This Works!    
    }
}

Is there a way to type cast the objects in the for-loop to avoid writing two lines? Does swift permit this? Used to get this done fairly easily in Objective - C

for (XYZClass *result in results) {

}

However, I have not been successful in Swift. I’ve tried explicit-cast with no luck.

for result as XYZClass in results {
    //ERROR: Expected ‘;’ in ‘for’ statements
}

for result:AGSGPParameterValue in results {
    /* ERROR: This prompts down cast as 
    for result:AGSGPParameterValue in results as AGSGPParameterValue { }
    which in turn errors again “Type XYZClass does not conform to Sequence Type”
*/
}

Any help is appreciated

Daniel T. · Accepted Answer · 2014-12-03 22:46:15Z

7

Try this:

for result in results as [XYZClass] {
    // Do stuff to result
}

answered Dec 3, 2014 at 22:46

Daniel T.

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Comments

Aron · Accepted Answer · 2019-02-25 13:43:19Z

1

Depending on how you are using the for loop it may be instead preferable to use compactMap (or flatMap if you are before Swift 4.1) to map your objects into a new array:

let onlyXyzResults: [XYZClass] = results.compactMap { $0 as? XYZClass }

Now you have an array XYZClass objects only, with all other object types removed.

edited Feb 25, 2019 at 13:43

answered Jan 4, 2019 at 17:00

Aron

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