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For the most part, any parameter for a component is readable, not as many are writeable. You just have to make sure the input/output is the correct type of object.
In the case of the Text value for the Label field, the object type is a String and is read/writeable.
So you can either input a String
MyLabel.text = myStringVariable;
Or output the String value
var myOutputString:String = MyLabel.text;