NSMakeRange() to Range in Swift

Question

Created Mar ’20

Replies 5

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Hello, I'm porting some of my old code to Swift and I'm running in to a little issue. I'm trying to get a range but I cant seem to get it all to work.

My old Obj-C code was

NSData *subData = [xData subdataWithRange:NSMakeRange(32, 16)];

I'm not sure how to convert this to Swift 5. half-open range operator wont go in reverse. I tried

.subdata(in: (16..<32).reverse() )

But that did not work.

Thanks!

Answered by Claude31 in 411578022

I assembled this toy code to show:

let string = "abcdefghij";
let data = string.data(using: String.Encoding.utf8)
let r = 2..<5
let data2 = Data((data!.subdata(in: r)).reversed())
let string2 = String(data: data2, encoding: String.Encoding.utf8)
print(string2!)

Boost

Answer 1

Claude31 OP

Mar ’20

syntax is reversed()

.subdata(in: (16..<32).reversed () )

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Answer 2

ceh329 OP

Mar ’20

sorry, yes I tried reversed()

The error I get is ...

Cannot convert value of type 'ReversedCollection<(Range<Int>)>' to expected argument type 'Range<Data.Index>' (aka 'Range<Int>')

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Answer 3

Claude31 OP

Mar ’20

Accepted Answer

I assembled this toy code to show:

let string = "abcdefghij";
let data = string.data(using: String.Encoding.utf8)
let r = 2..<5
let data2 = Data((data!.subdata(in: r)).reversed())
let string2 = String(data: data2, encoding: String.Encoding.utf8)
print(string2!)

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Answer 4

ceh329 OP

Mar ’20

Awesome, thanks! I mis-read the docs on reversed(). I was under the impression that it returned the same data type.

Thanks again!

0

Answer 5

OOPer OP

Mar ’20

`NSMakeRange(32, 16)` makes a range of location: 32, length: 16. It does not mean something reversed.

The equivalent Swift code to your Objective-C code is:

var subData = xData.subdata(in: 32..<48)

Or, a little more simply:

var subData = xData[32..<48]

If your purpose is to convert your Objective-C code into Swift, `reversed` has nothing to do with it:

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