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Posts Tagged ‘Snippets’

Customizing toString()

September 8th, 2008 11 comments

When writing classes for a framework I usually put a custom toString method into important classes so that debugging becomes easier. Normally they would go like something along the lines of:

override public function toString():String {
	return "[ClassName]";
}

… Sometimes adding properties to the returned String that give back information about the class, e.g.

override public function toString():String {
	return "[ImageClass, size=" + _size + "]";
}

But writing them rigid like that is a disadvantage when you decide later to refactor class names. Admittedly it’s also not a very elegant way so I got the idea to take the class name that is returned by getQualifiedClassName(). The only problem is that getQualifiedClassName not only provides the type name but also the whole package String of the class. Regular Expressions to the rescue! After twiddling around with them for a while (I’m by no means a RegExp expert) I got my toString method into the shape that I desired:

override public function toString():String {
	return "[" + getQualifiedClassName(this).match("[^:]*$")[0] + ", size=" + _size + "]";
}

This way it matches the String returned by getQualifiedClassName with the Regular Expression [^:]*$ which checks from the right end for an arbitrary text up to the first occurring colon, but without including the colon. Taking the first element of the Array returned by match() and you got what you need!

A nice way of using this is when writing abstract classes that contain the toString method and any subclass can use that toString method without the need to override it … that is of course unless you want ot add other output information.