Binding sap.m.RadioButton

Hi folks,

how do I bind the selected property of sap.m.RadioButtons? I understood that I group them with the groupName property but I'm totally missing sth. like RadioButtonGroup to get the selected key or alike. sap.m.RadioButton does not even provide a key? Could someone give an example?

<RadioButton groupName="MyGroup" text="Option A" selected="true" />

<RadioButton groupName="MyGroup" text="Option B" />

Say my model looks like this: { currentOption: "A" } The alternative option would be the char "B". How to map this?

BR
Chris