CODEWITHSUNDEEP
objective-cobjective-c++
gabor
gabor

Reputation: 4359

How do I convert a NSString into a std::string?

I have an NSString object and want to convert it into a std::string.

How do I do this in Objective-C++?

Upvotes: 113

Views: 83100

Answers (3)

Bruno Bieri
Bruno Bieri

Reputation: 10256

As noted on philjordan.eu it could also be that the NSString is nil. In such a case the cast should be done like this:

// NOTE: if foo is nil this will produce an empty C++ string

// instead of dereferencing the NULL pointer from UTF8String.

This would lead you to such a conversion:

NSString *foo = @"Foo";
std::string bar = std::string([foo UTF8String], [foo lengthOfBytesUsingEncoding:NSUTF8StringEncoding]);

Upvotes: 15

JustSid
JustSid

Reputation: 25318

NSString *foo = @"Foo";
std::string bar = std::string([foo UTF8String]);

Edit: After a few years, let me expand on this answer. As rightfully pointed out, you'll most likely want to use cStringUsingEncoding: with NSASCIIStringEncoding if you are going to end up using std::string. You can use UTF-8 with normal std::strings, but keep in mind that those operate on bytes and not on characters or even graphemes. For a good "getting started", check out this question and its answer.

Also note, if you have a string that can't be represented as ASCII but you still want it in an std::string and you don't want non-ASCII characters in there, you can use dataUsingEncoding:allowLossyConversion: to get an NSData representation of the string with lossy encoded ASCII content, and then throw that at your std::string

Upvotes: 160

Marco83
Marco83

Reputation: 1191

As Ynau's suggested in the comment, in a general case it would be better to keep everything on the stack instead of heap (using new creates the string on the heap), hence (assuming UTF8 encoding):

NSString *foo = @"Foo";
std::string bar([foo UTF8String]);

Upvotes: 51

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