What is meant by D blocking of mobile?

Here's an idea that I've been aching for in several different

languages: method blocking.

I often create base classes that will have lots of different kinds of

derived classes. To avoid duplicating code, I put all the method

definitions in the base class, so that they can be inherited by the

derived classes that really need them. But not all of the derived

classes should have access to all of the methods in the parent class,

and I'd like to block them.

Take a look at this code:

class baseClass {

public void doSomething() {

...

}

public void doSomethingElse() {

...

}

}

class derivedClassA: baseClass {

public void doSomethingFun() {

}

}

class derivedClassB: baseClass {

block void doSomething();

public void doSomethingSilly() {

}

}

In this example, my base class has two methods: "doSomething()" and

"doSomethingElse()". The class derivedClassA inherits both of these

virtual functions, but the class derivedClassB specifically blocks the

use of the "doSomething()" function. Attempting to call this function

should result in a compiler error, not in a runtime exception.

In the past, I've used exceptions to define class hierarchies like

this. I'll define the methods that I need in the base class, and then

I'll overload those functions in the derived classes, something like

this:

class derivedClassB: baseClass {

public void doSomething() {

throw new Exception("Cannot call doSomething from a

derivedClassB object");

}

public void doSomethingSilly() {

}

}

But throwing exceptions is costly, and besides, I should be able to

know AT COMPILE TIME if I'm calling methods that shouldn't exist

anyhow.

I've been wishing for functionality like this for ages, and I can't

fathom why it isn't available. It seems like it would be easy to use

the "block" keyword to simply remove an entry from the v-table,

wouldn't it?

2

it is related to ringtones, not knowing the excat meaning.