从C函数返回NSString

Question

In iOS development, is it possible to use NSString and return it from a function?

eg

(NSString * ) foo {
  return @"";

} 

This is not an objective c method, just function

Answer 1

Yes, seeing as objective-c objects are just pointers, you can create a C function to return one:

NS_RETURNS_RETAINED NSString *myFunction() {
    return [[NSString alloc] init];
}

Notice the use of NS_RETURNS_RETAINED . This is a hint to ARC and the static analyzer that this function returns a retained value to the receiver, and that it's their responsibility to release it.

If you were returning an autoreleased value, try using NS_RETURNS_NOT_RETAINED instead.

Answer 2

Yes, but the syntax is different:

NSString *foo()
{
    return @"bar";
}

Answer 3

NSString *foo()
{
    const char* yourString = "bar";
    NSString* yourNSString = [NSString stringWithFormat:@"%s", yourString];

    return yourNSString;
}

Answer 4

Yes, why not? Check NSStringFromRect() and similar for a reference.