Multiplying variables and doubles in swift

swift variables double multiplication
bmoondesign picture bmoondesign · Jun 6, 2015 · Viewed 32.1k times · Source

I'm a designer looking into learning Swift and I'm a beginner.

I have no experience whatsoever.

I'm trying to create a tip calculator using basic code in Xcode's playground.

Here is what I have so far.

var billBeforeTax = 100
var taxPercentage = 0.12
var tax = billBeforeTax * taxPercentage

I get the error:

Binary operator '*' cannot be applied to operands of type 'Int' and 'Double'

Does this mean I can't multiply doubles?

Am I missing any of the basic concepts of variables and doubles here?

Answer

omoman picture omoman · Jun 6, 2015

You can only multiple two of the same data type.

var billBeforeTax = 100 // Interpreted as an Integer
var taxPercentage = 0.12 // Interpreted as a Double
var tax = billBeforeTax * taxPercentage // Integer * Double = error

If you declare billBeforeTax like so..

var billBeforeTax = 100.0

It will be interpreted as a Double and the multiplication will work. Or you could also do the following.

var billBeforeTax = 100
var taxPercentage = 0.12
var tax = Double(billBeforeTax) * taxPercentage // Convert billBeforeTax to a double before multiplying.

Related questions

Static vs class functions/variables in Swift classes?

The following code compiles in Swift 1.2: class myClass { static func myMethod1() { } class func myMethod2() { } static var myVar1 = "" } func doSomething() { myClass.myMethod1() myClass.myMethod2() myClass.myVar1 = "abc" } What is the difference between a static function and a class function? Which one …

Read More
When to use static constant and variable in Swift?

There are some posts for how to write code for static constant and static variable in Swift. But it is not clear when to use static constant and static variable rather than constant and variable. Can someone explain?

Read More
Why can the keyword "weak" only be applied to class and class-bound protocol types

When I'm declaring variables as weak in Swift, I sometimes get the error message from Xcode: 'weak' may only be applied to class and class-bound protocol types I was just wondering why keyword weak can only applied to class and …

Read More