C++ Constructor definition

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C++

class myClass
{
    int var1,var2;
    public:
       myClass(int a1, int b1) : var1(a1), var2(b1)
       {
       }
};

is this a valid constructor definition?

Thanks!

Posted 4-Oct-12 18:47pm

NexusNemesis

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Comments

Mohibur Rashid 5-Oct-12 0:52am

didnt you ask the same question in another thread?

pasztorpisti 6-Oct-12 8:11am

The same code appeared in another thread, there the question was the difference between ctor initializer lists and assignments in ctor body.

Mohibur Rashid 6-Oct-12 9:21am

The validity is automatically part of that discussion

4 solutions

Solution 2

Yes, and it is exactly the same as this question[^] that you asked yesterday. Instead of posting your exam questions here, why not re-read your course notes.

Posted 4-Oct-12 22:33pm

Richard MacCutchan

Solution 4

yeah its a perfectly valid ctor.

Posted 6-Oct-12 1:34am

vaibhavbvp

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**JF2015** · Accepted Answer · 2012-10-04T18:50:00

Solution 1

Yes this is valid C++ and it compiles - I tested it. The constructor allows setting var1 and var2 when creating an object of the myClass class.

Posted 4-Oct-12 18:50pm

JF2015

tushar_patil · Accepted Answer · 2012-10-04T23:42:00

hi,
Yes it is a valid Ctor. This is called the initialization list, here both the variables are getting initialized "var1(a1), var2(b1)". Its more optimized and faster than assigning the values in Ctor as given below.

C#

class myClass
{
    int var1,var2;
    public:
       myClass(int a1, int b1) 
       {
          var1 =a1; 
          var2 =b1;
       }
};

Also this is the only way to assign values to the constant class variables in c++. As the constant variables has to be initialized with the value (and must not be assigned) while defining it and C++ don't allow to initialize vars inside class definition.