c++ call constructor within another constructor of the same class

Question

I am using MinGW-w64 with 4.8.1 (with -std=c++11) and trying to call one constructor of my class within another constructor of the same class. Unfortunately, I failed to compile the code below.

A::A(const char *pc) {
  A(string(pc));
}

A::A(string s) {
  vector<string> tmpVector;
  tmpVector.push_back(s);
  A(tmpVector);
}

// Constructor
A::A(vector<string> filePathVector) {
}

Below is the error GCC is complaining about.

In file included from ../parser/nsn/parser.h:37:0,
             from main.cpp:2:
../parser/nsn/parserimp.h: In constructor 'A::A(std::string)':
../parser/nsn/parserimp.h:522:29: error: conflicting declaration 'A  tmpVector'
  A(tmpVector);
                         ^
 ../parser/nsn/parserimp.h:520:17: error: 'tmpVector' has a previous declaration as   'std::vector<std::basic_string<char> > tmpVector'
  vector<string> tmpVector;

I've read about delegated constructor concept in C++11 but I am not sure this is what I am after....

juanchopanza · Accepted Answer · 2014-06-11 05:15:43Z

27

This

A(tmpVector);

is the same as this

A tmpVector; // but there is already an object called tmpVector

This explains the error. It looks like you want to call another constructor to initialize the same object. In this case you can use delegating constructors:

A::A(string s) : A(vector<string>{s})
{
}

Note that this was one of the latest C++11 language features to be added to the most popular compilers, so it may not work if your compiler doesn't have full C++11 language support.

edited Jun 11, 2014 at 5:15

answered Jun 11, 2014 at 5:07

juanchopanza

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14 Comments

Remy Lebeau Over a year ago

How is A(tmpVector); the same as A tmpVector;?

Fantastic Mr Fox Over a year ago

Both over 100k rep. This is an epic battle of the titans.

M.M Over a year ago

@RemyLebeau more info, stackoverflow.com/questions/24116817/…

M.M Over a year ago

similar case; void f(int s); is the same as void f(int (s));, this is the source of a lot of most-vexing-parse cases

Remy Lebeau Over a year ago

@MattMcNabb: I asked a separate question about the parenthesis issue and got a detailed answer with quotes from the standard that include the terms you mentioned.

|

fnisi · Accepted Answer · 2014-06-11 23:52:07Z

1

Thanks all, this is the final code, which was compiled smoothly by using mingw-w64 with GCC 4.8.1

A::A(const char *p) : A(string(p)) {
}

A::A(string s) : A(vector<string>{s}) {
}

A::A(vector<string> filePathVector) {
 // Do stuff here
}

edited Jun 11, 2014 at 23:52

answered Jun 11, 2014 at 23:21

fnisi

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