How Can I Replace Complex If Condition With Some Design Pattern ?

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1.00/5 (1 vote)

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Suppose i have nested if condition like arrow

C#

if()
{
   if()
      if()
        .....
        .....


}
else
{
}

How can I replace above problem with design pattern or some elegant approach
i have heard something about rule engine but don't know how to implement

Posted 23-Oct-14 9:14am

Naser Hassan

Updated 23-Oct-14 10:20am

CHill60

v2

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Sergey Alexandrovich Kryukov 23-Oct-14 15:36pm

The well-known concept of "design pattern" is about much less fine-grain, much wider scale features.
What's wrong with just reading the language manual and reference?
—SA

2 solutions

Solution 2

Even the question is answered and an answer is accepted...
If you are really interested to learn these "boolean" stuff I suggest to dive into it's Background.

E.g. you can start here: http://en.wikipedia.org/wiki/Boolean_algebra[^]

To know the Background also avoids to write silly staemanets like one can see often:

C#

bool theDecision= a && b;
if (theDecision == true) // silly to compare a boolean like this
{
    // this and that
}

Posted 23-Oct-14 10:43am

User 11060979

Updated 23-Oct-14 10:48am

v4

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Sergey Alexandrovich Kryukov · Accepted Answer · 2014-10-23T09:45:00

Solution 1

Please see my comment to the question. Such techniques are not related to "design patterns".

This is way too simple thing. Suppose you have

C#

if (conditionOne)
   if (conditionTwo)
      if (conditionTree)
          //...

It is strictly equivalent to

C#

if (conditionOne && conditionTwo && conditionTree) // in exactly this order
   //...

Note the use of '&&', which is not the same as '&'. '&&' optimizes out redundant condition check, exactly as with nested "if". In contrast to that, '&' will perform all the checks. Not only it would be worse for performance, if makes some difference in calculation if those conditions are properties with side effects (or they could functions, if I wrote conditionOne() instead of using the property syntax). That's why it is not recommended to create properties with side effect on getters; and even less recommended to use properties of functions with side effects in conditional operators. (I hope you understand what is "side effect": something except just returning the value).

Please see:
http://msdn.microsoft.com/en-us/library/2a723cdk.aspx[^],
http://msdn.microsoft.com/en-us/library/sbf85k1c.aspx[^].

—SA

Posted 23-Oct-14 9:45am

Sergey Alexandrovich Kryukov

Updated 23-Oct-14 10:29am

v3

Comments

Naser Hassan 23-Oct-14 16:10pm

i was looking some design pattern or technique by which i can make this code more readable and usable .lets say i want to use this conditions as rule what if my rule changed ,so wherever i have applied this rule needs modification

CHill60 23-Oct-14 16:22pm

Perhaps if you described your "rule engine" in a little more detail? As you have phrased your question, Sergey has already shown you how to make it more readable/elegant/accurate. Use the Improve Question link to give more detail perhaps?

PIEBALDconsult 23-Oct-14 16:23pm

Design Patterns won't help with that. If you want a better answer, ask a better question.

Sergey Alexandrovich Kryukov 23-Oct-14 16:24pm

I answered your question in full, didn't I?

If your rule need modification, the question is: during development of compile time? If development, just change the rules. Yes, make your code more readable. Just look at two equivalent form and decide by yourself what is readable and what not. For readability, consider breaking overly complex Boolean expressions into sub-expressions assigned to some local Boolean variables. I hope it's clear.

If runtime, use some Boolean properties or functions in the condition; they will return different Boolean values, depending on required factors. This are all your "patterns".

Will you accept it formally (green "Accept" button)? In all cases, your follow-up questions will be welcome.

—SA

Naser Hassan 23-Oct-14 16:34pm

i agree with your solution what you gave but i have many If's in my code one of which i asked ..sorry i am very new in software development so i don't know much

Sergey Alexandrovich Kryukov 23-Oct-14 16:50pm

No need to apologize; your questions will be very welcome.
Good luck, call again.
—SA