CODEWITHSUNDEEP
c++
Casper_2211
Casper_2211

Reputation: 1091

Passing a constructor to array of pointers

I have always been using vectors for storing objects when a list type container is required. I wanted to know how you can pass constructors to array pointers.The following works in C++03 if the object foo did not have a constructor

foo* p = new foo[5]()

Now what if the constructor of foo required an int how would I pass the constructor in the above statement?

Upvotes: 1

Views: 126

Answers (3)

Kerrek SB
Kerrek SB

Reputation: 477100

Since C++11, you can use brace initializers:

foo * p = new foo[5] { 1, 2, 3, 4, 5 };   // better: "auto p = ..."

This assumes that foo is implicitly constructible from int.

But you can just as well use containers:

std::vector<foo> v { 1, 2, 3 };
std::list<foo> w { 1, 2, 3 };

Or perhaps:

std::unique_ptr<foo[]> q(new foo[4] { 1, 2, 3, 4} );

Upvotes: 3

wilx
wilx

Reputation: 18228

It is not possible. Your foo instances can only be default-constructed.

UPDATE 1

If your foo does not have a default constructor then you will get a compiler error either about use of deleted function or about no matching ctor.

UPDATE 2

I see that others offer C++11 solution. My answer appears to be correct only for C++03 or earlier.

Upvotes: 3

Drew Dormann
Drew Dormann

Reputation: 63775

how would I pass the constructor in the above statement?

new[] does not have a form for forwarding constructor parameters.

You would instead call the constructors yourself.

foo* p = new foo[5]{ foo(1), foo(2), foo(3), foo(4), foo(5) };

Upvotes: 1

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