Abortive Validations

Someone deleted this, and maybe that's reasonable, but surely backlinks should be fixed at the same time, or the information left until it can be integrated or evaluated.

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This looks like another name for FailFast, or ExposeErrors -- PeteHardie

Or just simply GuardClauses

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If your method body contains several validations that abort (with possible error-handling code), and especially with nested if's, apply this Refactoring.

From (C# example):

if (overall valid)
{
if (valid Id)
{
if (valid Name)
{
� code to do work (all is valid) �
}
else
{
DebugLog?.AddValidationError?(�Bad Name�);
return false;
}
}
else
{
DebugLog?.AddValidationError?(�Bad Id�);
return false;
}
}
else
{
throw new Exception(�blah�);
}

To:

#region Validation Tests
if (!overall valid)
{
throw new Exception(�blah�);
}

if (!valid Id)
{
DebugLog?.AddValidationError?(�Bad Id�);
return false;
}

if (!valid Name)
{
DebugLog?.AddValidationError?(�Bad Name�);
return false;
}
#endregion

� code to do work (all is valid) �

Note that the validation test in the if statements are inverted. Here are the advantages:

• Saves excessive horizontal scrolling by eliminating nested indentation levels (code all fits on screen)
• Prevents common mistake: adding code to bottom of method (outside an else) that accidentally executes on a failed validation fall-through
• Locality: Places error code at the point of validation instead of burying it many lines below
• Can wrap validation code in a region and collapse it to reduce clutter/noise
• Improves overall clarity: can clearly see what code belongs to validation and what belongs to the work done

-- BrianG

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Better yet is to store all the errors on a stack and run your fail code if the stacksize is bigger than zero. (pseudo code):

errors = new errorStack;
if(!name){
errors->push('Name not ok');
}
if(!e mail){
errors->push('Email not ok');
}
  if(errors->size() > 0){
/* Fail code */
  } else {
/* Success code */
  }

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@Previous - That doesn't solve the problem of validation with nested ifs