Set objects to empty NSDictionary in Swift

Question

I can create an NSDictionary

    var namesDictionary=Dictionary<String,String>()
    namesDictionary["Jacob"] = "Marry"

But, when I create a empty dictionary like coded below, line 1 i okie, but line 2 (adding values) throws an error.

    var namesDictionary =[:]
    namesDictionary["Jacob"] = "Marry"

Error is "Cannot assign to the result of this expression". Is there any other way to assign the values.

Solution

It looks like it's an issue with swift interpreting the type of your dictionary. Try explicitly typing your empty dictionary.

var namesDictionary: Dictionary<String, String> = [:]
namesDictionary["Jacob"] = "Marry"

I think a better use for [:] is for emptying an already defined dictionary. If you add a third line namesDictionary = [:], you will be able to call namesDictionary["Jacob"] = "Marry" again since the compiler knows what type of dictionary it is from the inital declaration.

Comments

[NNikN]

Then it should have thrown error in the first line itself.

[Connor]

The first line is fine. It creates an empty dictionary, but the key/ value types aren't Strings. The dictionary at this point is pretty much useless since it won't accept any key value pairs

[NNikN]

Okie, what is the difference between the var namesDictionary=Dictionary<String,String>() and var namesDictionary: Dictionary<String, String> = [:]

[Connor]

Pretty much just syntactic sugar. Both create an empty Dictionary<String, String>

[NNikN]

namesDictionary.setValue("Marry", forKey: "Jacob") works

[Connor]

setValueForKey: is part of NSKeyValueCoding, not specific to dictionaries. If you call namesDictionary["jacob"] after it, you'll see it hasn't changed the dictionary