Objective-C++ converting std::string to NSString

Question

I would like to write an objective-C++ program in such a way that I could write:

class foo
{
public:
foo()
{
    bar = "Hello world";
}
std::string bar;
};

Then (below in the same .mm file) I could create an instance of that class then do something like:

@interface ViewController ()
@property (weak, nonatomic) IBOutlet UILabel *myLabel;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    foo* thisWontWork = new foo();
    self.myLabel.text = foo.bar; //this doesn't work obviously

// Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end

which would effectively change the text of label 'myLabel' to "Hello world"

oh, yeah that is a std::string :).. self.myLabel.text = @(thisWontWork->bar.c_str()) — Grady Player
– Grady Player, Commented Nov 5, 2015 at 19:13
do you want to copy the data in the string, or do you want an NSString that presents the data in the c++ string without taking ownership? — Richard Hodges
– Richard Hodges, Commented Nov 5, 2015 at 20:04
If theres another way that the below answer didn't cover I would be happy to see it! — user235236
– user235236, Commented Nov 5, 2015 at 23:31

trojanfoe · Accepted Answer · 2015-11-05 18:54:22Z

1

This should work:

self.myLabel.text = @(foo->bar.c_str());

Which converts std::string to const char * to NSString.

But note: you are leaking foo, so:

@interface ViewController ()
{
    foo _foo;
}
@property (weak, nonatomic) IBOutlet UILabel *myLabel;
@end

and use:

self.myLabel.text = @(_foo.bar.c_str());

edited Nov 5, 2015 at 18:54

answered Nov 5, 2015 at 18:49

trojanfoe

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2 Comments

user235236 Over a year ago

What do you mean leaking foo?

trojanfoe Over a year ago

@user235236 You are calling new and you never call delete.

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