Get first number of type CGFloat

Question

I have following numbers in CGFloat

375.0

637.0

995.0

I need to get the first number in CGFloat data type. For example the result for #1 must be 3.0, for #2 must be 6.0 and #3 must be 9.0

I tried the following

let width:CGFloat = 375.0
// Convert Float To String
let widthInStringFormat = String(describing: width)
// Get First Character Of The String
let firstCharacter = widthInStringFormat.first
// Convert Character To String
let firstCharacterInStringFormat = String(describing: firstCharacter)
// Convert String To CGFloat
//let firstCharacterInFloat = (firstCharacter as NSString).floatValue
//let firstCharacterInFloat = CGFloat(firstCharacter)
//let firstCharacterInFloat = NumberFormatter().number(from: firstCharacter)

Nothing seems working here. Where am I going wrong?

Update

To answer @Martin R, find below my explanation

I am implementing a grid-view (like photos app) using UICollectionView. I want the cells to be resized based on screen size for iPhone/iPad, Portrait and Landscape. Basically I don't want fixed columns. I need more columns for larger screen sizes and lesser column for smaller screen sizes. I figured that perhaps I can decide based on screen width. For example if the screen width is 375.0 then display 3 columns, If somewhere around 600 then display 6 columns, if around 1000 then display 10 columns and so on with equal width. So what I came up with is a) decide columns based on first number of the screen size and then for width divide by actual screen width. For example for a screen width of 375.0 I will have a cell size of CGSize(width: screenWidth / totalColumn) and so on.

possible duplicate? https://stackoverflow.com/questions/24085665/convert-string-to-float-in-apples-swift — Teetz, Jan 30 '18 at 13:11
@T.Werb tried that already not working. and it is not related — Ibrahim Azhar Armar, Jan 30 '18 at 13:13
@IbrahimAzharArmar why are you not using the property `firstCharacterInStringFormat` in the last 3 lines? — christopher.online, Jan 30 '18 at 13:14
I am curious: *Why* do you need that, what is the actual purpose? – And what should the result be e.g. for `-0.000123` ? — Martin R, Jan 30 '18 at 13:16
Is the input always the same format, so three numbers, a decimal point and then another number? In that case, divide by 100, and then use `floor`. — koen, Jan 30 '18 at 13:18
Is this a better way to describe your problem? ("I have a number of CGFloat values. I want to extract the largest magnitude decimal digit from each value as a separate decimal value." — Duncan C, Jan 30 '18 at 13:23
And, as Martin points out in his comment, you need to decide what to do if the value negative or if it's absolute value is less than one (in which case the first digit would probably be a zero.) — Duncan C, Jan 30 '18 at 13:24
@MartinR I updated my question to answer you. I don't need to deal with negative value because the screen size will not contain negative numbers. — Ibrahim Azhar Armar, Jan 30 '18 at 13:38
@Koen, @ Duncan C the input is actually the iPhone/iPad screen width which is always positive number. — Ibrahim Azhar Armar, Jan 30 '18 at 13:40
@MartinR also to address your other question for the example of `-0.000123` to me returning `0` seems a good solution. because I only asked for first digit regardless of any value on the right side of decimal. — Ibrahim Azhar Armar, Jan 30 '18 at 13:46
Re your update: What about a simple `let numColumns = (width/100.0).rounded()` ? — Martin R, Jan 30 '18 at 13:49

Pradeep Kashyap · Answer 1 · 2018-01-30T13:33:22.550

1

 var floatNum:CGFloat = 764.34
    var numberNeg = false
    if floatNum < 0{
        floatNum = -1.0 * floatNum
        numberNeg = true
    }
    var intNum = Int(floatNum)
    print(intNum) //764
    while (intNum>9) {
        intNum = Int(intNum/10)
    }
    floatNum = CGFloat(intNum)
    if numberNeg {
        floatNum = -1.0 * floatNum
    }
    print(intNum)//7
    print(floatNum)//7.0

try this one ...I hope it'll work

edited Jan 30 '18 at 13:33

answered Jan 30 '18 at 13:24

Pradeep Kashyap

921
10
15

That code would not handle negative numbers correctly. – Duncan C Jan 30 '18 at 13:26
@DuncanC i have updated the answer now it'll also work for negative number – Pradeep Kashyap Jan 30 '18 at 13:34
If the input is -764.34, should the result be 7 or -7 ? – koen Jan 30 '18 at 13:35
@PradeepKashyap this seems to do the trick, I actually don't have to deal with negaitve number but since you already have given the solution. Thank you. – Ibrahim Azhar Armar Jan 30 '18 at 13:43
Why not use `abs()` to get the absolute value? (There is a version of `abs()` for both floating point and integer types.) – Duncan C Jan 30 '18 at 13:48

score 1 · Accepted Answer · answered Jan 30 '18 at 14:01

You said:

For example if the screen width is 375.0 then display 3 columns, If somewhere around 600 then display 6 columns, if around 1000 then display 10 columns and so on with equal width.

So what you really want is not the first digit of the width (which would for example be 1 for width = 1024 instead of the desired 10) but the width divided by 100 and rounded down to the next integral value:

let numColumns = (width / 100.0).rounded(.down)

Or, as an integer value:

let numColumns = Int(width / 100.0)

Get first number of type CGFloat

2 Answers2