Macro to define javascript constructor keyword

Question

I have many classes which are like this:

struct A_Insert
{
    Data &d;
    A_Insert(d) : d(d){}

    // ...
}

struct A_Query
{
    Data &d;
    A_Query(d) : d(d){}

    // ...
}

struct B_Insert
{
    Data &d;
    B_Insert(d) : d(d){}

    // ...
}

struct B_Query
{
    Data &d;
    B_Query(d) : d(d){}

    // ...
}

The best thing I can think to do is define a macro like this:

#define Data_Query(name, body) struct name{Data &d; name(Data &d) : d(d) {} body}

but this leads to somewhat ugly code as I have to use parentheses to define my structs and my IDE doesn't handle it very well.

Data_Query(A_Insert, 
    int bind_params(stmt &stmt){}
    ...
)

I would like a macro which could allow me to get the name of the containing type for the constructor so I could write code like:

#define constructor CONTAINING_TYPE
#define Data_Construct Data &d; constructor (Data &d) : d(d) {}

struct A_Insert { Data_Construct // ... }

and this way my IDE could treat it like a normal struct declaration. Any suggestions would be appreciated.

it is the nature of macros that they lead to somewhat ugly code. It is not clear why you want to use a macro in the first place. — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Jul 27, 2020 at 11:51
@idclev463035818 it can sometimes be tedious to type out the name of the class for each new constructor. I would like if there was something like the javascript constructor keyword which define a constructor while making it easy to copy and paste and keeping the code very readable. I will add that to my question. — trinalbadger587
– trinalbadger587, Commented Jul 27, 2020 at 11:52
I don't see any reason for this. If you are using a halfway decent IDE it sure supports templates and auto complete. — Lukas-T
– Lukas-T, Commented Jul 27, 2020 at 11:57
@bipll true words, but I dare to claim that code with macros tends to be more ugly than code without — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Jul 27, 2020 at 12:00
No, it is not possible in C++. Of course almost everything is possible with macros, but where I work, it is only possible once. — n. m. could be an AI
– n. m. could be an AI, Commented Jul 27, 2020 at 12:03

user2039981 · Accepted Answer · 2020-07-27 12:12:32Z

2

Inheritance:

struct DataReference
{
    Data &d;
    
    DataReference(Data& d) : d(d) {}
};

struct A_Insert : DataReference
{
    using DataReference::DataReference;

    ...
};

answered Jul 27, 2020 at 12:12

user2039981

Sign up to request clarification or add additional context in comments.

5 Comments

Arthur Tacca Over a year ago

What is the purpose of using DataReference::DataReference;? This seems to pull the DataReference constructor into lookups within A_Insert, but it's already found there anyway. I don't see any purpose to it, am I missing something?

user2039981 Over a year ago

I don't know. But the compiler I use right now has a c++ version that doesn't automatically do that.

trinalbadger587 Over a year ago

@ArthurTacca I tried it without that and it didn't work. I don't really understand it but it seems to work.

Arthur Tacca Over a year ago

Ah I see: I thought that in the ... you were intending to declare another constructor that made use of DataReference's constructor. But actually you're suggesting that you don't write a constructor at all on the derived class at all. Instead, the using turns the DataReference(Data& d) into a A_Insert(Data& d) constructor automatically.

trinalbadger587 Over a year ago

This is the closest thing to what I wanted of having a constructor without having to write the declaring type because the 'using' doesn't require the name of the containing type.

Collectives™ on Stack Overflow

Macro to define javascript constructor keyword

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related