Signals & Slots stopped working

[gabor53]

Hi,
I have the following code which used to work:

    connect(ui->descr_TextEdit, &QTextEdit::textChanged, [this]()
    {
        description = getDescription ();
    });

Now it gives me the following error messages:

1. 'description' is not captured
2. the lambda has no capture default
3. QString 'description' declared here.

How can I fix this?
Thank you.

[Paul Colby]

Hi @gabor53,

Does your class still have a description member?

[gabor53]

Yes I have it.

[Paul Colby]

Can you show the actual compiler error output?

[gabor53]

Hi @Paul-Colby
Here is the complete error message:

C:\Programming\Projects\Folkfriends_1_0\additem.cpp:-1: In lambda function:
C:\Programming\Projects\Folkfriends_1_0\additem.cpp:254: error: 'description' is not captured
description = getDescription ();
^
C:\Programming\Projects\Folkfriends_1_0\additem.cpp:252: the lambda has no capture-default
connect(ui->descr_TextEdit, &QTextEdit::textChanged, this
^
C:\Programming\Projects\Folkfriends_1_0\additem.cpp:29: 'QString description' declared here
void Additem::Addcontent(QString name, QString newWhat, QString newMaterial, QString newColor, QString description, QString newmonth)
^

[VRonin]

replacing [this] with [&] works?

[kshegunov]

@gabor53
If description is a function parameter you must capture it explicitly:

void Additem::Addcontent(QString name, QString newWhat, QString newMaterial, QString newColor, QString description, QString newmonth)
{
    // ... 
    connect(ui->descr_TextEdit, &QTextEdit::textChanged, [this, description]()
    {
        description = getDescription();
    }); 
    // ...
}

But in any case such a capture is useless, because you can only do it by value.

[Paul Colby]

@Paul-Colby said:

Does your class still have a description member?

@gabor53 said:

Yes I have it.

void Additem::Addcontent(QString name, QString newWhat, QString newMaterial, QString newColor, QString description, QString newmonth)

That's not a class member.

Cheers.

[VRonin]

@kshegunov
From the compiler output Additem::Addcontent is at line 29 while the lambda is at line 252 so I doubt it's nested. It's just description missing as a class member full stop

[kshegunov]

@VRonin

so I doubt it's nested

At this point we can guess and bet.

It's just description missing as a class member full stop

Perhaps, or maybe the function is spanning 300 lines. The point is, without a more complete piece of the code we can't know for sure.

@gabor53

Do you mind sharing your class declaration and Additem::Addcontent function?

[gabor53]

@VRonin
Hi,
replacing [this] with [&] worked. Thank you.

[kshegunov]

@gabor53
Perhaps it compiles, but have you tested if it runs okay? Judging by the compile error and the solution, I'd be really surprised if you don't get a segfault. My previous request - to provide the whole function definition - stands.

[gabor53]

Hi @kshegunov
Here is the full code:
additem.h
Addcontent function
Thank you for your help.

[kshegunov]

@gabor53
You are hiding the class member with the function argument because they have the same name. I advise not to use the same name for local and class variables.

[jerome_isAviable]

1. 'description' is not captured
   said that in your lambda, 'description' has not been captured... then add it on the list of captured elements: [this, captured]
   I red inside the answers that you may declare same name for function and variable... don't do that, it will generate problems for sure.
2. QString 'description' declared here
   it is a clue for said that the answer of call this.getDescription() should be a QString (QString getDescription() const;)
   so 'description' has to be a QString (i think in private area of this). because you are not pass it, it is an undeclared new object inside your lambda function.

so give a varaible name unik and pass the variable inside your lambda by the array list [....] should fix your problem.