Create String object from std::string by overloading = operator

Question

I've tried several options but my compiler does not pick up the operator overloading or something else is wrong. I'm using XCode 4.5.2 with default Apple LLVM compiler 4.1.

The error I get is this: Assigning to 'cocos2d::CCString *' from incompatible type 'const char [5]'

on these lines:

CCString *s_piece__locks = "TEST";
cocos2d::CCString *s_piece__locks2 = "TEST";

My .h code:

CCString& operator= (const std::string& str);
//    CCString& operator= (const char* str);  // this doesn't work either
const CCString& operator = (const char *);

My .cpp code (even though this is irelevant):

CCString& CCString::operator= (const std::string& str)
{
    m_sString = CCString::create(str)->m_sString;
    return *this;
}

const CCString& CCString :: operator = (const char* str)
{
    m_sString = CCString::create(str)->m_sString;
    return *this;
}

Your help is very appreciated, thanks!

Based on the error message, you're trying to assign the char[] into a pointer to CCString. — Angew is no longer proud of SO
– Angew is no longer proud of SO, Commented Jan 10, 2013 at 12:21
@Angew oops, your comment was not there when I started writing the answer. — Masked Man
– Masked Man, Commented Jan 10, 2013 at 12:25

Masked Man · Accepted Answer · 2013-01-10 12:36:31Z

1

The error message Assigning to 'cocos2d::CCString *' from incompatible type 'const char [5]' suggests that you are assigning a char array to a pointer to cocos2d::CCString.

This should work:

char bar[] = "ABCD";
cocos2d::CCString foo;
foo = bar;

edited Jan 10, 2013 at 12:36

answered Jan 10, 2013 at 12:24

Masked Man

1

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6 Comments

leftaroundabout Over a year ago

Actually, that would use a copy constructor though, not copy assignment operator.

PerfectGamesOnline.com Over a year ago

I got it, I use it with the pointer variable but the declaration is for a static object, correct? I should add another operator for the pointer CCString *foo = "ABCD", hope it is possible :-(

Masked Man Over a year ago

@leftaroundabout Ah, you are right. Overlooked that, sorry. Let me edit.

Masked Man Over a year ago

@devZone.touchDude.com Why not just dereference the pointer and be done with it?

PerfectGamesOnline.com Over a year ago

@Deidara-senpai: I'm converting lot's of code from objectiveC and I want to keep code which has say CCString *str; as class property and I want to use this->str = "test" as assignmen, if possible. Still trying to make this happen but no success yet.

|

leftaroundabout · Accepted Answer · 2013-01-10 13:00:23Z

CCString *s_piece__locks = "TEST";
cocos2d::CCString *s_piece__locks2 = "TEST";

What the heck is this supposed to do? Declaring a pointer does not generate any object except the pointer itself. So basically, for this to "work", there would need to be another CCString object around already, that happens to represent the string "TEST". But even if that's given, how is C++ supposed to know which one to point to? It would need to look "TEST" up in some kind of e.g. hash map.

None of this makes any sense. Change your code to either

Direct use of object on stack:

cocos2d::CCString s_piece;
s_piece = "TEST";

Assigning new content to an object that resides somewhere else. You'd normally use a reference for this, e.g.
```
void assign_test_to(cocos2d::CCString& target) {
  target = "TEST";
}
```
it's also possible with a pointer
```
void assign_test_to_ptr(cocos2d::CCString* target) {
  *target = "TEST";
}
```
but don't do that unless you have a specific reason to.

In principle, there's another possibility:

cocos2d::CCString* s_piece_locks = new CCString;
*s_piece_locks = "TEST";

but you want to avoid this, as it can very easily lead to memory leaks. What would be ok is

std::unique_ptr<cocos2d::CCString> s_piece_locks = new CCString;
*s_piece_locks = "TEST";

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