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Posts Tagged ‘Vacation Budgeter’

Xcode’s Next Top Model

September 7, 2015 Leave a comment

The idea seemed simple enough. An app to keep track of your budget on vacation. You’d launch the app and then… what? Okay, I can figure that out later. 

First a bit of triage. iOS apps are generally designed around a Model-View-Controller pattern. The idea is pretty simple. Your app has to do three basic things. First, it has to have some data, stored in a predictable format (the model). It has to show you things on the screen (the view). Finally it should be able to manipulate the model and view (the controller), making sure that the right data is displayed, and that as the user manipulates the objects on screen, that’s being translated correctly back to the data. 

For my needs, the model seem like the easiest bits to address, so I’m going to start there. 

Well, it’s a a budget app, so there’s going to be a budget object. That can be fairly simple to start with. It’ll have a name, a start date, an end date, a total, and some line items. What do those line items look like? Well, since the user can customize them, I don’t want to get too clever. So an array of budget items it is. In Swift, your  budget template will look something like this:

    internal var budgetItems: [VacationBudget.NWDBudgetItem]

 

    internal var name: String

 

    internal var startDate: NSDate?

 

    internal var endDate: NSDate?

 

    internal var tripLength: Int? { get } // We can figure this out since we know the start date and end date

 

Wait, what is an NWDBudgetItem? Well, that’s a good question. Well, it’s gotta have a name, which can be a String, and it’s gotta have a value, which can be an Int. No, that won’t work. In America, at least, we still have fractions of a dollar to worry about (you might know them as those those little metal discs that seem to end up strewn about your home). We’ll want a better way to represent a value. My plan is to use a struct that knows how many cents it has, but can give you the amount in dollars, cents, whatever floats your boat. 

What you get might look like:

public typealias Cent = Int

public typealias Dollar = Int

 

struct NWDValue {

 

    internal var dollars: NWDValue.Dollar { get set }

 

    internal var cents: NWDValue.Cent { get set }

 

    internal var totalCents: NWDValue.Cent { get }

 

    /// returns “\(self.dollars).\(self.cents)”

    internal var stringValue: String { get }

 

    mutating internal func setTotalCents(cents: Cent)

}

 

You, dear reader, may be a professional programmer and you may be looking at this and listing off the many ways in which this is a bad idea, and I’ll end up back at the drawing board before this whole thing is over. That may be the case, but hey, at least it will give me some blog fodder as I try to fix the mess I am getting myself into. 

This is… well, it’s a good start. But the bigger challenge is going to be figuring out exactly how the user will interact with this thing. Next time: You Gotta Start Somewhere

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