MixedStaticInstanceThisAccess.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>
<overview>
<p>
A method of a class can be either a static method or an instance method.
For a static method, the value of <code>this</code> is the enclosing class.
For an instance method, the value of <code>this</code> is the object instance itself.
It is therefore not possible to refer to a static method from an instance method using <code>this</code>, and vice versa.
</p>

</overview>
<recommendation>

<p>
A reference to an instance method from within a static method needs to be qualified with an instance of the class, and not <code>this</code>.
</p>

</recommendation>
<example>

<p>
In the following code snippet, the <code>bar</code> method is an instance method and it attempts to use the static <code>baz</code> method through <code>this</code>.
That is not possible, so the call will fail at runtime.
</p>

<sample src="examples/staticInstance.js" />

<p>
The code should be changed to use the enclosing class instead of <code>this</code>: <code>Foo.baz(42)</code>.
</p>

</example>
<references>

<li>Mozilla Developer Network: <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/static">Classes and static methods</a>.</li>

</references>
</qhelp>