Developing API methods to return JSON

Question

When developing API methods to return JSON with details I often find myself creating the following code:

 $response = array('success' => false);
 $user = User::getSessionUser();
 if($user->id > 0){
 if(ItemSKU::stringIsValid($sku)){
 $itemSKU = ItemSKU::getFromString($sku);
 if($itemSKU->isAvailable()){
 if(Carts::add($user->id, $sku)){
 $response['success'] = true;
 }
 else{
 $response['error'] = "Item was already added";
 }
 }
 else{
 $response['error'] = "Unavailable Item";
 }
 }
 else{
 $response['error'] = "Invalid SKU";
 }
 }
 else{
 $response['error'] = "Invalid User";
 }
 return response()->json($response);

How can I avoid using this nested if-else chain?

• Drakes: Your logic flow is easy to follow. No problems here.

Answer 1

Personally I prefer avoiding such nested if-else constructs, simply by reversing the logic, e.g.:

if(!cond1)
 return value;
if(!cond2)
 return value2;
// etc.

instead of:

 if (cond1)
 if(!cond2)
 return value2;
 else
 return value;

• Machavity: Yeah, if you have tons of conditions a return statement is your friend, since it has the same net effect as the if block

Answer 2

You can check for the error conditions first, and immediately return if they're true:

$response = array('success' => false);
$user = User::getSessionUser();
if(!($user->id > 0)){
 $response['error'] = "Invalid User";
 return response()->json($response);
}
if(!ItemSKU::stringIsValid($sku)){
 $response['error'] = "Invalid SKU";
 return response()->json($response);
}
$itemSKU = ItemSKU::getFromString($sku);
if(!$itemSKU->isAvailable()){
 $response['error'] = "Unavailable Item";
 return response()->json($response);
}
if(Carts::add($user->id, $sku)){
 $response['success'] = true;
}
else{
 $response['error'] = "Item was already added";
} 
return response()->json($response);