How to Load a Dictionary into a UIPickerView

Question

How can I load data from a dictionary into a PickerView in Swift?

I have dictionary with a String key (States) and a Double value (taxes) and what I want to do is be able to set the keys as the titleForRow of the UIPickerView and show the value of the selected key in a textField.

// Ideal Dictionary
private var states:[String:Double] = ["Alabama":6.000, "Illinois":7.000, "Oregon":8.000, "Wisconsin":9.000]

I was able to do what I described above using two arrays, one for the states and one for the taxes but I refuse to think that loading from a dictionary is not possible.

Here is what I currently have that works but using two arrays.

// Arrays
private var stateName = ["Alabama", "Illinois", "Oregon", "Wisconsin"]
private var stateTax = ["6.000", "7.000", "8.000", "9.000"]

func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return stateName.count
}
func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    inputTaxRate.text = stateTax[row]
}
func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    return stateName[row]
}

Any suggestion to improve the above code?

Answer 1

Dictionaries are unordered, so you are better off using an array. You can use an array of named tuples to keep your data together in one array:

let stateInfo:[(name: String, tax: Double)] = [("Alabama", 6.000), ("Illinois", 7.000), ("Oregon", 8.000), ("Wisconsin", 9.000)]

func pickerView(pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    return stateInfo.count
}

func pickerView(pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
    inputTaxRate.text = stateInfo[row].tax
}

func pickerView(pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
    return stateInfo[row].name
}

Answer 2

You could use a dictionary, but a dictionary has no order. You want your data to be ordered. If the order is alphabetical order, you would effectively turn your dictionary into the same two arrays you have now. You wouldn't want to do that repeatedly that on every call to titleForRow so you would want the arrays to be permanent. That being so, your two arrays turn out to be a pretty good solution. You are fetching the data with ruthless efficiency and that's just what you want.