Calculate width and height of AttributeText does not correct - ios

Question

I'm making an app chat and I have a problem with the chat message's size.
I've calculate my message's height like this and I've got the correct height
maximumMessageWidth = 300.0
let size = CGSize(width: maximumMessageWidth, height: 1000.0)
let messageAttributeText = messageBody.attributedText
let height = messageAttributeText?.boundingRect(with: size, options: .usesLineFragmentOrigin, context: nil).height
To avoid the special case like this image. I have to calculate the width
It has the big space after my message
I want it to look like this:
This is the code I use to calculate the message width (I used the correct height which I've calculated the width)
let size = CGSize(width: 1000.0, height: height)
let messageAttributeText = messageBody.attributedText
var width = messageAttributeText?.boundingRect(with: size, options: .usesLineFragmentOrigin, context: nil).width
but width in this code seem not right. Because I think it does care about my height property. It assume that my text is in only 1 line.
But I want to calculate the width, so that my text will `fill the whole label' just like the second image
Does anyone know how to calculate the width in my case ?

Answer 1

You can do that by casting String to NSString
var string = "Hello, World"
let nsString = string as NSString
let size = nsString.size(attributes: [NSFontAttributeName: UIFont.systemFont(ofSize: 14)])
The size will give you width and height of the string.
You can apply this to your NSAttributedStrings string property.

Answer 2

After a bit of research, I find out this:
The calculate width code doesn't work right because it do not care about the height property.
If height = 100 or height = 1000 it will return the same result because it assume to draw all the text in just one line.
So to calculate the width, I used binary search
var minWidth:CGFloat = 0.0
var maxWidth = maxWidth
while true {
if (minWidth >= maxWidth) {
width = minWidth
break
}
let testWidth = (maxWidth + minWidth) / 2.0
if calculateMessageHeight(width: testWidth) > messageHeight {
minWidth = testWidth + 2.0
continue
} else {
maxWidth = testWidth - 2.0
continue
}