I get error: incompatible pointer types initializing 'NSMutableArray *' with an expression of type 'NSArray?

Question

NSMutableArray *sortedReleases = [theReleases sortedArrayUsingComparator:^(id a, id b)

I get the following:

Incompatible pointer types initializing 'NSMutableArray *' with an expression of type 'NSArray *'

I have to have sortedReleases as a NSMutableArray. How do I get past it?

Thanks

Matt Lacey · Accepted Answer · 2011-12-12 04:12:52Z

6

This should do the trick I think (written in browser) — NSMutableArray inherits from NSArray, so you can use the arrayWithArray constructor.

NSMutableArray *sortedReleases = [NSMutableArray arrayWithArray:[theReleases sortedArrayUsingComparator:^(id a, id b)]]

answered Dec 12, 2011 at 4:12

Matt Lacey

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Comments

Stripes · Accepted Answer · 2011-12-12 04:50:45Z

1

sortedArrayUsingComparator returns a NSArray*, you want a NSMutableArray*. In ObjC the mutable types inherit from the immutable types, so you can't just use the NSArray*. You need something to take your NSArray* and give you the equivolent NSMutableArray*. In this case the NSMutableArray arrayWithArray method will do it.

Try something like:

NSMutableArray *immutableSortedReleases = [theReleases sortedArrayUsingComparator:^(id a, id b)...]
NSMutableArray *sortedReleases = [NSMutableArray arrayWithArray:immutableSortedReleases];

Or if sufficiently clear, skip having immutableSortedReleases, and put the arrayWithArray call inline.

edited Dec 12, 2011 at 4:50

answered Dec 12, 2011 at 4:33

Stripes

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