Using a function’s return value as an if condition, good practice

coding-standardsconditionsconventionsprogramming practices

Do you think it is a good practice to use function return values as if conditions? I'm coding in PHP atm but it holds for many other languages.

if(isTheConditionMet($maybeSomeParams))
{
}

$res = isTheConditionMet($maybeSomeParams);
if($res)
{
}

I can't think of a situation where the first one creates a problem, can it?

EDIT: Assume return value is not going to be used after condition is evaluated.

Best Answer

In the code you posted, there's no reason to store the function result in a variable before using it. (Unless perhaps the name of the variable is sufficiently meaningful that it makes the code clearer to the reader.)

On the other hand, if you need to refer to the value more than once, you should probably store it in a variable rather than calling the function multiple times, which could be inefficient and/or wrong:

$res = isTheConditionMet($maybeSomeParams);
if ($res)
{
    echo "res = $res\n";
    // do stuff
}

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For example a void InsertRow() method could throw an exception if there already exists a row with the same key. The question is, is it reasonable to assume that the caller ensures their row is unique before calling InsertRow? If the answer is no, then I'd also provide a bool TryInsertRow() which returns false if the row already exists. In other cases, such as db connectivity errors, TryInsertRow could still throw an exception, assuming that maintaining db connectivity is the caller's responsibility.

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Just copy one of the functions from this Stack Overflow post on retrieving values from a query string, and reuse it in your JavaScript code, such as this function:

function getParameterByName(name) {
    name = name.replace(/[\[]/, "\\[").replace(/[\]]/, "\\]");
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There's nothing wrong with pulling parameters from the query string in your JavaScript code as long as you are not executing anything you get from the query string. The JavaScript equivalent of htmlspecialchars is here.

However, if the $id was not coming from the query string, lets say it was coming directly from your server, it would be fine to echo it into your HTML and access it from JavaScript. (Try pressing ctrl-u now and see this page's HTML).

Best Answer

Related Solutions

C# Programming Practices – When and Why to Use Void Instead of Bool/Int

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