Simple calculation in Swift2

Question

Just trying my first simple attempt on a calculation in swift2, but I can't seem to get it right. I have a UITextField input called ValueA I want to du the following calculation on that input (i can have decimals) (((ValueA * ValueA)+3)*1.36) The result must return a number with up to two decimals. I have tried the following:

let kw = 1.36
let three: Double = 3
var a: Double = NSString(string: ValueA.text!).doubleValue
var b: Double = NSString(string: ValueB.text!).doubleValue
var answer:Double = (((a * a) + three) * kw)
let answerFormatter = NSNumberFormatter()
answerFormatter.minimumFractionDigits = 2
answerFormatter.maximumFractionDigits = 2
let Ranswer = answerFormatter.stringFromNumber(answer)!
Result.text = Ranswer`

It kindda works, but sometimes my simulator crashes and sometimes it gets me the right answer but with more decimals as zeroes eg: 45.23000000 (instead of 45.23)

Can someone clean up my code? The answer need to go back into a textfield. Remember I am a total newbee in swift :)

What is the stacktrace you get from the simulator crash? Could you post it here? — vrwim
– vrwim, Commented Jun 23, 2016 at 6:57

Community · Accepted Answer · 2017-05-23 12:08:26Z

1

You can use something like this

let kw = 1.36
let three: Double = 3
var a = Double(ValueA.text!)!
var b = Double(ValueB.text!)!
var answer = (((a * a) + three) * kw)


 let Ranswer = String(format:"%.2f", answer)
Result.text = Ranswer

And are you sure you wanna do a * a? and not a * b. Just making sure, because you arent using b anywhere

you can also use

let Ranswer = Double(round(100 * answer)/100)
Result.text = String(Ranswer)

Source of information : link

edited May 23, 2017 at 12:08

CommunityBot

11 silver badge

answered Jun 23, 2016 at 9:31

user6248853

Sign up to request clarification or add additional context in comments.

4 Comments

Eiko Over a year ago

Multiplying and dividing by 100 is no appropriate method to format a floating point number. Formatting with some format specifier is. :)

user6248853 Over a year ago

@Eiko I'm with you on this! I'm not the original one to answer this. But I included this because I absolutely love the creativity of the guy who came up with this method (credits to him through the link) I have changed the answer though, thanks for pointing out!

KristianC Over a year ago

Can't make it work. Build fails. It should be a*a. I have not made the code where b is used, yet :)

user6248853 Over a year ago

Why would the build fail? share the error? and also the code that you tried

Code Different · Accepted Answer · 2016-06-23 13:44:30Z

0

You are assuming that the always enter a valid number into ValueA and ValueB. That's one possible source for the crash. Better check that the text can be converted to numbers.

Try this (not tested):

let kw = 1.36
let three = 3.0

if let a = Double(ValueA.text!), b = Double(ValueB.text!) {
    let answer = (((a * a) + three) * kw)

    let answerFormatter = NSNumberFormatter()
    answerFormatter.minimumFractionDigits = 2
    answerFormatter.maximumFractionDigits = 2

    let Ranswer = answerFormatter.stringFromNumber(answer)!
    Result.text = Ranswer
} else {
    print("You must enter a number into ValueA and ValueB")
}

answered Jun 23, 2016 at 13:44

Code Different

93.4k16 gold badges154 silver badges175 bronze badges

2 Comments

KristianC Over a year ago

That worked perfect. I had made the UITextfields as show numeric keyboard, så that is why I didn't check for numerics values. Where does the Print go? I can't see it anywhere in the simulator? Is there anyway to use comma in this calculation? eg 5,5 instead of 5.5? When I use comma nothing happens

Code Different Over a year ago

I think Double uses the default separator for your locale when converting string to number. Use NSNumberFormatter if you want to customize that. print will go to the Debug Console. Press Cmd + Shift + Y to open it

Collectives™ on Stack Overflow

Simple calculation in Swift2

2 Answers 2

4 Comments

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related