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Can Constructor argument have value assigned to it?

Posted on 2013-06-11
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Last Modified: 2013-06-11
class UsbSocket : public Socket
{
  public:
   
    struct USBStatus
    {
      char txReady       : 1;
      char rxReady       : 1;
      char hw_connected  : 1;
      char connected     : 1;
      char suspended     : 1;
      char rxRetry       : 1;
      char txFull        : 1;
    };

    /// <summary>Constructor
    /// </summary>
    UsbSocket(unsigned short tId = 0);



In above constructor,  is argument assigned value of 0.  Can value be passed to this constructor?
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Question by:naseeam
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5 Comments
 
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Accepted Solution

by:
evilrix earned 266 total points
ID: 39238831
A constructor is just a function (all be it a slightly special one) and, yes, it can have a default value just like any other function can.

In your example the default value for the parameter is, indeed, zero but you can override that by passing an explicit argument yourself.
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Author Comment

by:naseeam
ID: 39238889
What's the use of assigning default value when it will be overridden when the functions is called?
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Assisted Solution

by:evilrix
evilrix earned 266 total points
ID: 39238898
Well, it doesn't have to be. The idea is it's a sensible default but it gives you, the consumer of that class, the ability to override it. For example, a bank account class might default to a balance of zero but it could be constructed with a balance of more than zero if the customer was planning on paying in at the same time the account is opened.
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Author Comment

by:naseeam
ID: 39238950
What will be the syntax of the function call if customer makes the call with default argument?
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Assisted Solution

by:jkr
jkr earned 134 total points
ID: 39239181
The syntax would be like

UsbSocket a(2); // explicit argument
UsbSocket b; // default argument

Open in new window


or

UsbSocket* pa = new UsbSocket(2); // explicit argument
UsbSocket* pb = new UsbSocket; // default argument

Open in new window

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