operator<< QString

[kiker99]

Hello,

i'm sure someone had the same problem before. I am trying to make one of my classes able to receive "<<"-Operations. this is my code:

// messagepipe.h
 friend void operator<<(MessagePipe *pipe, QString string);
 
//messagepipe.cpp
void operator<<(MessagePipe *pipe, QString string)
{
     //do something
}

// messagepipe.h
 friend void operator<<(MessagePipe *pipe, QString string);

//messagepipe.cpp
void operator<<(MessagePipe *pipe, QString string)
{
     //do something
}

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MessagePipe is my class. This produces an error if used like this:

MessagePipe *hint;
hint << "Hi there.";

MessagePipe *hint;
hint << "Hi there.";

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--> error: invalid operands of types 'MessagePipe*' and 'const char [10]' to binary 'operator<<'

Hm, he isn't able to get a QString out of "Hi there". This seems to work only if used as a real parameter. Does anybody understand this behaviour? I don't want to write everytime QString("My Text"). Any ideas? Thanks.

[wysota]

Try "const QString &" instead of QString.

[kiker99]

Try "const QString &" instead of QString.

thanks for the fast reply, but this doesn't change anything here
Is this supposed to help or are you guessing?

[shad]

'const QString&' should help.
my original posting was incorrect

[kiker99]

'const QString&' should help.
my original posting was incorrect

code looks like this now.

// messagepipe.h
friend void operator<<(MessagePipe *pipe, const QString& string);
 
// messagepipe.cpp
void operator<<(MessagePipe *pipe, const QString& string)
{
	pipe->message(string);
}

// messagepipe.h
friend void operator<<(MessagePipe *pipe, const QString& string);

// messagepipe.cpp
void operator<<(MessagePipe *pipe, const QString& string)
{
	pipe->message(string);
}

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the error is still exactly the same.
I even recompiled the project, but that didn't help either.

[orb9]

Make the pointer a reference and it should work. You could also return the pipe to allow chaining.

// messagepipe.h
friend MessagePipe& operator<<(MessagePipe &pipe, const QString& string);
 
// messagepipe.cpp
MessagePipe& operator<<(MessagePipe &pipe, const QString& string)
{
	pipe.message(string);
        return pipe;
}

// messagepipe.h
friend MessagePipe& operator<<(MessagePipe &pipe, const QString& string);

// messagepipe.cpp
MessagePipe& operator<<(MessagePipe &pipe, const QString& string)
{
	pipe.message(string);
        return pipe;
}

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[kiker99]

yihaa, thx a lot @orb9. I had to change everything for references, but now it is working

to tired to think about the reason for this...