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How do I get a char * of the string stored in the String class? [message #97]

Thu, 24 November 2005 10:29

jeff1101
Messages: 11
Registered: November 2005
Location: Philippines

Promising Member

How do I get a char * of the string stored in the String class?

The String class doesnt have a method like .c_str() or .chars()

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Re: How do I get a char * of the string stored in the String class? [message #102 is a reply to message #97]

Thu, 24 November 2005 12:01

gprentice
Messages: 260
Registered: November 2005
Location: New Zealand

Experienced Member

From looking at String source code, it stores a null at the end of a string and has an operator funciton returning const char * so you can actually just use your string object anywhere a const char * is needed - or you could explicitly cast it.

(Maybe Mirek can confirm the null termination is always there ...)

void gp1(const char * p)
{
PromptOK(p);
}

void HelloWorld::About()
{
PromptOK("{{1@5 [@9= This is the]::@2 [A5@0 Ultimate`+`+ Hello world sample}}");

String abc = "hello";
gp1(abc);
}

Graeme

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Re: How do I get a char * of the string stored in the String class? [message #103 is a reply to message #97]

Thu, 24 November 2005 12:09

gprentice
Messages: 260
Registered: November 2005
Location: New Zealand

Experienced Member

And I just noticed the squiggle operator returns a const char * so you don't need to cast get a const char *.

void gp1(const char * p)
{
	PromptOK(p);
}


void HelloWorld::About()
{
	PromptOK("{{1@5 [@9= This is the]::@2 [A5@0 Ultimate`+`+ Hello world sample}}");

	String abc = "hello";
	gp1(~abc);
}

Graeme

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Re: How do I get a char * of the string stored in the String class? [message #105 is a reply to message #102]

Thu, 24 November 2005 13:35

mirek
Messages: 14290
Registered: November 2005

Ultimate Member

Yes, you can always cast to "const char *" and be always sure there is terminating 0.

BTW, this cast is implicit, so as long as there are no ambiguities, you can just write

String q;
....
const char *s = q;

operator~ is there to solve ambiguities usually resulting from overloading.

Note that U++ string does not support non-const char * access - this is because such thing would break COW implementation strategy. If you need to change individual characters of String, you can use Set method or StringBuffer. Note also that using StringBuffer instead of String is slightly faster in situations where you "building" String out of individual characters (and it then can be easily converted to String in low-cost operation).

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Re: How do I get a char * of the string stored in the String class? [message #113 is a reply to message #97]

Fri, 25 November 2005 04:05

jeff1101
Messages: 11
Registered: November 2005
Location: Philippines

Promising Member

Wow, thanks a lot. Razz

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