Why does this code in Swift produce an empty row on NSTableView? - cocoa

Question

I'm (obviously) new to Swift, and I'm new to Cocoa programming in general. When I build this code and run it, it automatically inserts an empty row on the NSTableView for peopleList[0], so when I go to add a new person, they show up in the second row, and the first remains empty. I'm at a loss as to why this is. I know I can probably remove the blank row programmatically before inserting the first row of data, but I'd like to know the root cause of this if possible.
Here is my code:
import Cocoa
class AppDelegate: NSObject, NSApplicationDelegate, NSTableViewDataSource, NSTableViewDelegate {
#IBOutlet var window: NSWindow
// Table View Outlet
#IBOutlet var tableViewData : NSTableView
// Text Field Cell Outlets
#IBOutlet var firstNameTextField : NSTextField
#IBOutlet var lastNameTextField : NSTextField
#IBOutlet var ageTextField : NSTextField
#IBOutlet var netWorthTextField : NSTextField
// declare an array of multiple dictionaries
var peopleList = [Dictionary <String, String>()]
func applicationDidFinishLaunching(aNotification: NSNotification?) {
// Insert code here to initialize your application
}
func applicationWillTerminate(aNotification: NSNotification?) {
// Insert code here to tear down your application
}
func numberOfRowsInTableView(aTableView: NSTableView!) -> Int
{
let numberOfRows:Int = getDataArray().count
return numberOfRows
}
func tableView(tableView: NSTableView!, objectValueForTableColumn tableColumn: NSTableColumn!, row: Int) -> AnyObject!
{
var newString = getDataArray().objectAtIndex(row).objectForKey(tableColumn.identifier)
return newString;
}
func getDataArray() -> NSArray {
return peopleList
}
// When button is hit, add NSTextField values to array and refresh the tableview
#IBAction func addFieldDataToArray(sender : AnyObject) {
peopleList.append(["FirstName": firstNameTextField.stringValue, "LastName": lastNameTextField.stringValue, "Age": ageTextField.stringValue, "NetWorth": netWorthTextField.stringValue])
println(peopleList)
tableViewData.reloadData()
}
}

Answer 1

This is happening because of the way you're initializing and appending to peopleList. Upon initialization, peopleList is an array of Dictionary<String, String> and contains a single empty dictionary:
> var peopleList = [Dictionary <String, String>()]
[[String : String]] = 1 value {
[0] = {}
}
After adding a person, it looks like this -- you've appended a new person's information, but that empty initial dictionary is still there.
[[String : String]] = 2 values {
[0] = {}
[1] = {
[0] = {
key = "NetWorth"
value = "About 10 bucks"
}
[1] = {
key = "LastName"
value = "Schmoe"
}
[2] = {
key = "Age"
value = "37"
}
[3] = {
key = "FirstName"
value = "Joe"
}
}
}
I'd recommend starting out with peopleList completely empty -- no empty row to worry about:
> var peopleList: [Dictionary<String, String>] = []
[[String : String]] = 0 values