NSArray Equivalent of Map

Question

Given an NSArray of NSDictionary objects (containing similar objects and keys) is it possible to write perform a map to an array of specified key?

Answer 1

There is a special key-path operator for this: @unionOfObjects. Probably it replaced [collect] from previous versions.

Imagine a Transaction class with payee property:

NSArray *payees = [self.transactions valueForKeyPath:@"@unionOfObjects.payee"];

Apple docs on Array Operators in Key-Value coding.