Shall I use the structs as a Parameterized Constructor in C++?

Question

This is my sample code. I used it like this, but I had an error from //error-line.

The following error appeared:

Variable has incomplete type 'std::TestCpp:: TestString'

class TestCpp{
    public:
        any value;
        struct TestString;

        TestCpp(TestString Value){ // error
            this->value = static_cast<any>(Value);
            cout << Value;
        }

};

Because you are using the object ``Value`` in your function. And the compiler does not know anything about it. You want to define your function after ``struct TestString`` is defined. — sz ppeter, Feb 05 '20 at 07:31
This might be helpful for you https://stackoverflow.com/questions/23279810/passing-a-struct-as-a-constructor-parameter-in-c — Paul, Feb 05 '20 at 07:35
I Just want to set the Value's datatype as a TestStrin(struct) @StoryTeller-UnslanderMonica — Ambrose Jesuraj, Feb 05 '20 at 08:51
I defined the TestString below the TestCpp class.@MichaelChourdakis — Ambrose Jesuraj, Feb 05 '20 at 08:51

score 1 · Accepted Answer · answered Feb 05 '20 at 07:43

1

You are using an instance of TestString in the constructor of TestCpp before it has been defined. You should first define TestString, then define the constructor of TestCpp. My guess is you don't want to define TestString where you declared it. To achieve that, you can do this by defining the constructor of TestCpp in a source file for instance.

// header file
struct TestCpp
{
    std::any _value;
    struct TestString;
    TestCpp(TestString); // declare here, define in source file    
};

// source file
#include "header_file"

struct TestCpp::TestString { /* ... */ };

TestCpp::TestCpp(TestString) { /* ... */ }

answered Feb 05 '20 at 07:43

mfnx

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How to I directly use the TestCpp struct inside the parameterized constructor of TestCpp. – Ambrose Jesuraj Feb 05 '20 at 08:57
And also I have one doubt, Shall I declare a Struct inside the source file – Ambrose Jesuraj Feb 05 '20 at 08:58
No. how to use the TestCpp struct inside a C++ class file constructer. – Ambrose Jesuraj Feb 05 '20 at 08:59
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/207252/discussion-between-mfnx-and-ambrose-jesuraj). – mfnx Feb 05 '20 at 09:03
Got a Answer from @mfnx. – Ambrose Jesuraj Feb 05 '20 at 09:32

Shall I use the structs as a Parameterized Constructor in C++?

1 Answers1