how can I create two dynamic objects with overloaded constructor?

Question

Please look the code below, it's a simple subject but I don't know.

class trial{
public:
    trial(){
        y = -1;
    }
    trial(int x){
        y = x;
    }
public:
        int y;
};


int main() {
    trial *trialPtr = new trial();     // creates a dynamic object with empty constructor
    trial *trialPtr1 = new trial(1);   // creates a dynamic object with overloaded constructor
    trial *trialPtr2 = new trial[2];   // creates two dynamic objects with empty constructor
    return 0;
}

My question is, how can I create two dynamic objects with overloaded constructor?

parapura rajkumar · Accepted Answer · 2011-11-16 01:18:41Z

3

This is not possible with an built in array

However consider using a std::vector

vector<trial> var(10, trail(4));

This has the added benefit that you don't need worry about memory management

Adding an ugly solution because OP apparently wants it. Set FOO to appropriate value before creating the array. Please read comments before downvoting

int FOO = -1;

class trial{
public:
    trial(){
        y = FOO;
    }
    trial(int x){
        y = x;
    }
public:
        int y;
};

int main(int argc, _TCHAR* argv[])
{
    FOO = 4;
    trial *trialPtr2 = new trial[2];
    return 0;
}

edited Nov 16, 2011 at 1:18

answered Nov 16, 2011 at 1:09

parapura rajkumar

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2 Comments

Cihad Turhan Over a year ago

@parapura, thanks for quick answer. However, for my project it's not allowed to used any built-in dynamic/static arrays, I must do it by using pointers. Can't we find any solution?

Kerrek SB Over a year ago

Vectors are always a Good Thing, but the traditional vector constructors are only good for either copying an existing range or for filling everything with the same value. C++11 also lets you initialize vectors from a brace-list, with arbitrary content: std::vector<std::string> v { "mom", "jim", "ezekiel" };.

Kerrek SB · Accepted Answer · 2011-11-16 01:11:33Z

2

Arrays are problematic in C++98/03, because you can't generally initialize them entirely freely. C++11 fixes this through uniform initialization. Now you can say,

new trial[2] { 1, 1 };

answered Nov 16, 2011 at 1:11

Kerrek SB

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2 Comments

Cihad Turhan Over a year ago

Ah this is not working :( test.cpp:22: warning: extended initializer lists only available with -std=c++0x or -std=gnu++0x </br> test.cpp:22: error: ISO C++ forbids initialization in array new test.cpp:22: error: no matching function for call to 'trial::trial(<brace-enclosed initializer list>)'

Kerrek SB Over a year ago

@CihadTurhan: As I said, it's a C++11 feature. With GCC, add -std=c++0x to the command line (or -std=c++11 in GCC 4.7+).

djhaskin987 · Accepted Answer · 2011-11-16 01:13:18Z

0

There is no syntactic way to do this in C++, as in this (incorrect) example: trial *trialPtr2 = new trial2; You must do a "for" loop if you wish to use an array:

trial *trialPtr2[] = new (*trial)[2];
for (int i = 0; i < 2; i++)
{
    trialPtr2[i] = new trial(3);
}

answered Nov 16, 2011 at 1:13

djhaskin987

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