Respond to an unknown method call: Difference between revisions

=={{header|Fantom}}==

In Fantom, you can call methods statically or dynamically. Static calls to methods will be checked at compile time. Dynamic method calls (indicated by an <code>instance->method</code> syntax) are run through a "[http://fantom.org/doc/sys/Obj.html#trap trap]" method at run time, and can thus be caught:

<lang fantom>

class A

{

// override the 'trap' method, which catches dynamic invocations of methods

override Obj? trap(Str name, Obj?[]? args := null)

{

echo ("In trap, you called: " + name + " with args " + args.join(","))

return null

}

}

class Main

{

public static Void main ()

{

a := A()

// note the dynamic dispatch

a->methodName (1, 2, 3)

}

}

</lang>

Output:

<pre>

$ fan unknown-method.fan

In trap, you called: methodName with args 1,2,3

</pre>

In normal usage, the trap method tries to locate the named method using reflection on the current class.