由于类型String不符合协议IntervalType而导致Swift for-in循环错误

Question

I am working on a Swift iOS application. I am getting the compile error in for-in loop. Please check the code below, not sure why is this error throwing here?

var listDict : Dictionary = ["Insurance":"home", "Saving":"MutualFund"]
for valueName in listDict {

    switch valueName {

        case "Insurance":
            println("My insurance mname")
        default:
            println("Defualt")
    }        
}

and compile error I got is,

Type String doesn't conform to protocol IntervalType

Answer 1

valueName is a tuple, you therefore need to access one of its elements - either the key or value in this case. Taking your example:

for valueName in listDict {
    switch valueName.0 {
    case "Insurance":
        print("Value = \(valueName.1)")
    default:
        print("Defualt")
    } 
}

Or, which I personally think is more readable:

for (key, value) in listDict {
    switch key {
        case "Insurance":
            println("Value = \(value)")
        default:
            println("Default")
    }
}

Answer 2

Try this

var listDict : Dictionary = ["Insurance":"home", "Saving":"MutualFund"]
for valueName in listDict.keys {

    switch valueName {

    case "Insurance":
       println("My insurance mname")
    default:
       println("Defualt")
   }

}

Here you will traverse through all keys of your dictionary, which you intend to do according to your case statement.

in your code, you're trying to traverse key:value pairs. I suspect, error arise once compiler reaches case - it is trying to compare String to Tuple, which is not known how to do.

Answer 3

As pointed out already, the structure you should expect is a tuple.

You can easily check what is the type of a variable (if not explicitly stated) by clicking on the "Quick help" in your Xcode project.

As you can see the type of valueName is (String, String) .