Hi Andrea:
You asked what some of the "defaults" were doing in the API; and I had
a look at them today while cleaning up 2.6.x. In particular we have a
few places where constants are defined in order to document what
options are available.
Michael I am determined to make the library easier to use; mostly
using our tutorials as a stick to beat useful methods in (or useless
methods out) where we can. This is our first example ...
interface Font {
/**
* @param style The "font-style" SVG parameter (one of "normal",
"italic", or "oblique"
*/
void setStyle( Expression style );
...
/** An enumeration of font style values
*/
interface Style {
static final String NORMAL = "normal";
static final String ITALIC = "italic";
static final String OBLIQUE = "oblique";
}
}
These are a pain to use out of the box without:
- making them an actual enumeration which implements Literal; or
- adding a setStyle( String style ) method; or
- font.setStyle( filterFactory.literal( Font.Style.NORMAL ) )
For reference here is what making this a real enum would look like
(allowing font.setStyle( Font.Style.NORMAL ) to be used directly)
/**
* Enumeration of allow font-style values.
* <p>
* This is a way to document the constants allowable for the setStyle method
*/
enum Style2 implements Literal {
NORMAL("normal"),
ITALIC("italic"),
OBLIQUE("oblique");
final String literal;
final static int count=0;
private Style2(String constant) {
literal = constant;
}
public Object accept(ExpressionVisitor visitor, Object extraData) {
return visitor.visit( this, extraData );
}
public Object evaluate(Object object) {
return literal;
}
public <T> T evaluate(Object object, Class<T> context) {
// return Converters.convert(literal, context);
if( context.isInstance( literal) ){
return context.cast(literal);
}
return null;
}
public Object getValue() {
return literal;
}
}
There are two problems
- the location of the converter API (it is part of main); perhaps we
can move it to api for more general usefulness
- you cannot provide an implementation of equals or hascode for an
enumeration (so I need to use a CodeList)
It may be easier to provide these as static final ConstantExpressions
rather than group them into enumerations as has been done here.
Jody
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