Read variables between more than 2 forms
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[quote author="avmg" date="1403203760"]Also i add the next line to the .pro file to use the nullptr:
QMAKE_CXXFLAGS += -std=c++0x
[/quote]
This is not portable and will cause an error when used with compiler like MSVC. Use this instead:
@
CONFIG += c++11
@As for the segfault - well then you're "doing something wrong"™ ;) Most likely calling setForm1Ptr on an uninitialized form2 pointer. Start your debugger and check. I'm not really good at "guess debugging" ;)
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[quote author="avmg" date="1403204829"]Does the f1 name be the same as the created at the begginig or it doesn't matter?[/quote]
I don't think I understand. f1 is the pointer to the first form. It's a member of Form2 class. I'm just using placeholder names. You can (and should) name them something meaningful.The sequence of events should be as follows:
- you create a Form1 instance (form1)
- somewhere (eg. in the constructor of Form1) you create instance of Form2 (form2)
- somewhere(eg. right after the above) you use form2->setForm1Ptr to set pointer to form1 (f1) inside form2
- somewhere in form2 you use that pointer f1 to get data from form1
If you do it in any other order it will likely result in a segfault.
For example call to form2->setForm1Ptr when form2 is not yet created will segfault.
Using f1 before it was set will segfault.
Using f1 after form1 was destroyed will segfault.
Calling form2->setForm1Ptr after form2 was destroyed will segfault.
You get the picture ;)[quote author="avmg" date="1403204829"] if i not debug the program crashes and show on the application output: The program has unexpectedly finished.[/quote]
That means you've got a bug. That's what you use a debugger for ;) -
Hi again,
Finally i understood how to send data between forms and i could continue with my program. But i'm again in another trouble related with the same. I want to get a struct declared in another form. I did like this to get the struct:
// Form1.h
Public slots:
mystruct return_struct(void);Private:
struct mystruct{
...
}mystruct new_mystruct;
// Form1.cpp
mystruct return_struct(void){
return new_mystruct;
}I've declared new_mystruct in Form1.h to have access to this data on every functions of this form. The problem is that it says in the Form1.h return_struct function:
'mystruct' does not name a type.
I think i should create new_mystruct on the Form1.cpp constructor but if i do this, i have not access to this on the functions...
What do you recommend me?
Thanks -
Please use code tags when posting code (last button on the right). It's easier to read.
You haven't posted entire code but from what I see you declared your struct in the private section of Form1. As so it is not visible to outside classes and the compiler is right - there is no 'mystruct' outside of Form1.
You need to declare it in a public section and refer to it as mystruct when inside Form1 members and as Form1::mystruct anywhere outside.Btw. It's a good convention to start type names with capital letter. That way people know right away what is what.
As for where you create an instance of it. You don't say what the struct contains but if you return a local variable like you did you don't get chance to fill it with any meaningful data. So either fill it up with something before you return or make it a class member and fill it elsewhere.
Example:
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//Form1.h
class Form1 {
public:
MyStruct {
...
}
MyStruct getStruct() const;private:
MyStruct structInstance;
};//Form1.cpp
Form1::MyStruct getStruct() const { return structInstance; }//Somewhere else
Form1* form1 = ... //form1 is some instance of Form1
Form1::MyStruct data = form1->getStruct();
@
You can use structInstance in any of the Form1 members this way.Edit: Oh, and it's not an error, but it's unusual for a getter function to be a slot. Slots are meant as functions that modify your object in a reaction to a signal. They're not meant to return values as there is no object to give that value to in a connect statement. Getters like yours should not be slots.
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Sorry, getStruct is a class member function. I missed class specifier:
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Form1::MyStruct Form1::getStruct() const { return structInstance; }
@ -
Hi again!
Before i ask how to get the struct from another form. Now i'm trying to set values from a struct located in another form. The question is that the struct is too to make a set function for each variable...so i was thinking on this two options, considering that in Form2 I have a private struct that I want to change from Form1.
1- Try to send the complete struct. I declared a second struct in Form1, i modify the values and i send to Form2, once i receive there i change the values. But i don't have declared the struct in Form1 and also i think is a very ugly solution.
2-Try to make a pointer in Form1 to the struct located in Form2 to modify it.
Anyway both solutions are ugly, and i want to know a good way to do it.
Thanks.
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You mean you have 2 structs in both forms and they look the same? Why not just declare it once outside of both classes?
From design standpoint if both forms are reading and writing to it then it clearly doesn't belong to any of them. -
I got a private struct in a Form, and if i want to change it from another Form i have to implement a public function like "set_value", but if the struct is too big and i don't want to add let's say 200 functions, i need to do something diferent. Finally i create a temporal struct in form1, after i modify the values i want, and finally i send this struct to the form2 where is declared the struct i wanted to modify at the begining.
If i declare outside i can't access because is private.
For sure there are many ways and better but this is the best i could done actually...
