Question

I tried

scala> class Foo extends Component { var font = new java.awt.Font("Helvetica", java.awt.Font.BOLD, 12) }

and I got:

<console>:10: error: overriding variable font in class Component of type java.awt.Font;
 variable font needs `override' modifier
       class Foo extends Component { var font = new java.awt.Font("Helvetica", java.awt.Font.BOLD, 12) }
                                         ^ 

So I tried

scala> class Foo extends Component { override var font = java.awt.new Font("Helvetica", java.awt.Font.BOLD, 12) }

but this didn’t help at all:

<console>:10: error: overriding variable font in class Component of type java.awt.Font;
 variable font has incompatible type
       class Foo extends Component { override var font = new java.awt.Font("Helvetica", java.awt.Font.BOLD, 12) }
                                                  ^

What’s the reason behind this error and how should it be done correctly?

EDIT: Sorry, didn’t saw that scala also has Component. The Component in question is the one from java.awt.Component!

Answer 1

Component contains getters and setters for font, so the canonical way to set the font is:

class Foo extends Component {
  font = new java.awt.Font(/* blah blah */)
}

If you want to override the font defs to use a var, you have to use something compatible with scala.swing.Font, which wraps the Java fonts (normally done with implicit conversions). Like so:

class Foo extends Component {
  override var font: scala.swing.Font =
    new java.awt.Font("Helvetica", java.awt.Font.BOLD, 12)
}

I’m not sure this will do what you want. (Edit: tested in a REPL session with too much junk loaded; you don’t actually need to do this! The simple override var font = new java.awt.Font thing works.) The normal getter/setter is designed to pass the information on through to the javax.swing peer. If you do it this way, you’ll probably break that forwarding. So use the first method.

---

Edit if you are trying to do this in a java.awt.Component: Font font; is a private field in java.awt.Component. You can’t override fields in Java, and you can’t do anything with private fields in Java. So trying to override it with a new var is guaranteed to not work. (The compiler could certainly give a more informative error message, however!) Scala can only override fields because they’re not really fields–they’re a getter/setter pair referring to a hidden underlying field.

You should use (or override) getFont and setFont instead.