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gauard clause in java

Posted on 2014-10-02
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Last Modified: 2014-10-05
Hi,

I am going through below link

http://refactoring.com/catalog/replaceNestedConditionalWithGuardClauses.html

I see below code can be modified better as given further below
double getPayAmount() {
  double result;
  if (_isDead) result = deadAmount();
  else {
    if (_isSeparated) result = separatedAmount();
    else {
      if (_isRetired) result = retiredAmount();
      else result = normalPayAmount();
    };
  }
  return result;
};  

double getPayAmount() {
  if (_isDead) return deadAmount();
  if (_isSeparated) return separatedAmount();
  if (_isRetired) return retiredAmount();
  return normalPayAmount();
};  

Open in new window


I wonder what is the meaning of 'guard clause'  what is its significance.

Please advise
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Question by:gudii9
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4 Comments
 
LVL 34

Assisted Solution

by:ste5an
ste5an earned 167 total points
ID: 40358314
"Guard Clause" means that you exit the code by an early return, avoiding the "evaluation" of the further else parts.
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LVL 27

Assisted Solution

by:dpearson
dpearson earned 166 total points
ID: 40358340
You might find this example:
http://blog.mafr.de/2009/06/12/a-case-for-guard-clauses/

easier to understand.  It points out more clearly exactly what the "guard clause" is in the code.  It's "guarding" the later code from being executed, because some condition has not been met.  So you can edit the function immediately.

Hope that helps,

Doug
0
 
LVL 7

Author Comment

by:gudii9
ID: 40358618
double getPayAmount() {
  if (_isDead) return deadAmount();
  if (_isSeparated) return separatedAmount();
  if (_isRetired) return retiredAmount();
  return normalPayAmount();
};  

Open in new window


In above code where and how they are doing

"Guard Clause" means that you exit the code by an early return, avoiding the "evaluation" of the further else parts.

Please advise
0
 
LVL 37

Accepted Solution

by:
zzynx earned 167 total points
ID: 40358821
What is your remaining question exactly?

These are the three guard clauses:

  if (_isDead) return deadAmount();
  if (_isSeparated) return separatedAmount();
  if (_isRetired) return retiredAmount();

Open in new window


If the variable _isDead is true, we immediately return deadAmount()
If the variable _isSeparated is true, we immediately return separatedAmount()
If the variable _isRetired is true, we immediately return retiredAmount()

That's much better readable and understandable than the first code you posted
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