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iOS Swift 2.0 Collections and Control Flow Dictionaries Recap: Dictionaries

Jeff Bennion
Jeff Bennion
406 Points
Posted by Jeff Bennion
Jeff Bennion
406 Points

There was a discussion months ago about this being a confusing question: is [3] an index or array. Why isn't it fixed?

Apparently the question was written assuming [3] is an index, which would make the answer false. However, it seems that it could also be a key, which would make the answer true. This question was asked 5 months ago, and I'm wondering why the question has not been fixed or removed

1 Answer

Anjali Pasupathy
Anjali Pasupathy
28,883 Points
Anjali Pasupathy
Anjali Pasupathy
28,883 Points

dict is shown to be a Dictionary in the line above it, which uses the updateValue:forKey: function, a function specifically for Dictionary types. Because of this, [3] must be a key; anything else would indicate that dict is not a dictionary, which would make the question pointless.

The question is asking whether or not updateValue:forKey: does the same thing as adding or changing a key-value pair in a Dictionary with subscripting; the answer to that question is no, they're not the same action. Subscripting just adds or changes the key-value pair; it doesn't return anything. updateValue:forKey:, on the other hand, returns the old value if the key currently exists in the Dictionary, or nil otherwise.

I hope this helps!