How does initializing inherited members inside base class constructor reduce the calls to…?


T

trubar a

I’ve at the following link

http://books.google.com/books?id=VGT1_UJzjM0C&lpg=PP1&dq=pro c# 2008&pg=PA193#v=onepage&q&f=false

that instead of initializing inherited members ( _c1 in our example )
inside derived constructor:

class A
{
public int _c;
}

class B:A
{
public B(int c)
{
_c = c;
}
}

we should initialize them inside base class constructor, since that
way we reduce the calls to inherited members ( _c ):

class A
{
public A(int c)
{
_c = c;
}
public int _c;
}

class B:A
{
public B(int c)
: base(c)
{


}
}

If _c field is initialized inside base constructor, the order of
initialization is the following:

1) First the field initializers of derived class B are called
2) Then field initializers of base class A are called (at this point
_c is set to value 0)
3) B’s constructor is called, which in turn calls A’s custom
constructor
4) _c field gets set to value of a parameter c ( inside A’s custom
constructor )
5) Once A’s custom constructor returns, B’s constructor executes its
code.

If _c field is initialized inside B's constructor, the order of
initialization is the following:

1) First the field initializers of a derived class B are called
2) Then field initializers of a base class A are called(at this point
_c is set to value 0)
3) B’s constructor is called, which in turn calls A’s default
constructor
4) Once A’s custom constructor returns, B’s constructor sets _c field
to a value of parameter c

As far as I can tell, in both cases _c was called two times, so how
exactly did we reduce calls to inherited member _c?

thanx
 
Ad

Advertisements

A

Arne Vajhøj

I’ve at the following link

http://books.google.com/books?id=VGT1_UJzjM0C&lpg=PP1&dq=pro c# 2008&pg=PA193#v=onepage&q&f=false

that instead of initializing inherited members ( _c1 in our example )
inside derived constructor:

class A
{
public int _c;
}

class B:A
{
public B(int c)
{
_c = c;
}
}

we should initialize them inside base class constructor, since that
way we reduce the calls to inherited members ( _c ):

class A
{
public A(int c)
{
_c = c;
}
public int _c;
}

class B:A
{
public B(int c)
: base(c)
{


}
}

If _c field is initialized inside base constructor, the order of
initialization is the following:

1) First the field initializers of derived class B are called
2) Then field initializers of base class A are called (at this point
_c is set to value 0)
3) B’s constructor is called, which in turn calls A’s custom
constructor
4) _c field gets set to value of a parameter c ( inside A’s custom
constructor )
5) Once A’s custom constructor returns, B’s constructor executes its
code.

If _c field is initialized inside B's constructor, the order of
initialization is the following:

1) First the field initializers of a derived class B are called
2) Then field initializers of a base class A are called(at this point
_c is set to value 0)
3) B’s constructor is called, which in turn calls A’s default
constructor
4) Once A’s custom constructor returns, B’s constructor sets _c field
to a value of parameter c

As far as I can tell, in both cases _c was called two times, so how
exactly did we reduce calls to inherited member _c?

I think the entire performance discussion is utterly irrelevant.

Fields should be private and they should be initialized in
the class that declares them.

Arne
 
K

kndg

[...]
I think the entire performance discussion is utterly irrelevant.

Fields should be private and they should be initialized in
the class that declares them.

Arne

Totally agreed!
I wonder why people make simple thing complicated.
 
M

Mike Schilling

Arne Vajhøj said:
I think the entire performance discussion is utterly irrelevant.

Fields should be private and they should be initialized in
the class that declares them.

In other words, the rule is about encapsulation, not about performance.
 
A

Arne Vajhøj

In other words, the rule is about encapsulation, not about performance.

At least if as the case here where the performance difference
must be almost unmeasurable.

Arne
 
Ad

Advertisements

Ad

Advertisements


Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Top