Merge two Dictionaries - ios

Question

I have a dictionary like this. It's a set of parameters to be set in a HTTP body.
let parameters = [ "UserCredentials": [ "Personalnumber": personalNo, "Password": password ], "DeviceCredentials": ["UniqueId": uniqueId] ]
The type inference output of the parameters variable is [String : Dictionary<String, String>].
What I want to do is instead of creating this dictionary explicitly, I want to build it. As in have functions to create each section of it and finally merge them all to have the final output as the original one shown above.
func deviceCredentials() -> [String: [String: String]] {
return ["DeviceCredentials" : ["UniqueId": "1212121212"]]
}
func userCredentials(pnr: String, password: String) -> [String: [[String: String]]] {
let personalNo = ["Personalnumber": pnr]
let password = ["Password": password]
return ["UserCredentials": [personalNo, password]]
}
I have two separate methods to create each section.
I don't know how to merge the output from these two because their output types are different.

Answer 1

You'll need to create the merger function yourself that will loop through both dictionaries and combine them into one. I think the reason Apple wouldn't provide that function is what if there's a conflict (same key is present in both dictionaries)?
For what you want to do, I think it may be easier to create an NSMutableDictionary and then pass it as a parameter to both functions so that each of them can add the objects it needs to add.

Answer 2

Because your inner-most dictionaries vary in type, you will need to use AnyObject when you define your outermost dictionary and downcast when you retrieve the items as necessary. You can also return a tuple instead of a Dictionary to make it easier to build your outermost dictionary -
func deviceCredentials() -> (key:String, value:[String: String]) {
return ("DeviceCredentials",["UniqueId": "1212121212"])
}
func userCredentials(pnr: String, password: String) -> (key:String, value:[[String: String]]) {
let personalNo = ["Personalnumber": pnr]
let password = ["Password": password]
return ("UserCredentials", [personalNo, password])
}
var dict=Dictionary<String,AnyObject>()
let deviceCreds=deviceCredentials()
dict[deviceCreds.key]=deviceCreds.value
let userCreds=userCredentials("user", "password")
dict[userCreds.key]=userCreds.value
However, you can change the structure of your userCredentials value slightly and use -
func deviceCredentials() -> (key:String, value:[String: String]) {
return ("DeviceCredentials",["UniqueId": "1212121212"])
}
func userCredentials(pnr: String, password: String) -> (key:String, value:[String: String]) {
var retDict=Dictionary<String,String>()
retDict["Personalnumber"] = pnr
retDict["Password"]= password
return ("UserCredentials", retDict)
}
var dict=Dictionary<String,Dictionary<String,String>>()
let deviceCreds=deviceCredentials()
dict[deviceCreds.key]=deviceCreds.value
let userCreds=userCredentials("user", "password")
dict[userCreds.key]=userCreds.value