/** Represents the <code>null</code> value in the EllaScript language. */
public class NullImpl extends AbstractObj implements NativeObj, Null {
public static int OBJECT_ID = ProtoRegistry.generateObjectID();
/** A hint to the type this null value was intended to have. */
public final Class<?> typeHint;
/** Creates a new null value. */
public NullImpl() {
this(null);
}
/**
* Creates a new null value with the given class indiciating it's intended type.
*
* @param typeHint the type hint.
*/
public NullImpl(Class<?> typeHint) {
this.typeHint = typeHint;
}
/**
* NOTE: Undefined variables in scripts will have the null value (Null.instance) assigned. NOTE:
* With specifying a special constructor for the Null object we ensure nothing is created NOTE:
* out of null. TODO: Maybe we should throw an expception instead of just returning null...
*/
protected static final NativeCall NATIVE_CONSTRUCTOR =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args) throws ClosureTerminatedException {
return engine.getObjNull();
}
};
public Class<?> getTypeHint() {
return typeHint;
}
public int getObjectID() {
return OBJECT_ID;
}
/**
* Registers this EllaScript object within the given execution context.
*
* @param ctx the execution context to register this object in.
*/
public static void registerInContext(Context ctx) {
NullProto.registerInContext(ctx);
ctx.registerProto(OBJECT_ID, NullProto.OBJECT_ID);
if (!ctx.hasObject(OBJECT_ID)) {
ctx.registerObject(new NullImpl());
}
}
public Call getNativeConstructor() {
return NATIVE_CONSTRUCTOR;
}
@Override
public Object toJavaObject() {
return null;
}
public String toString() {
return "Null";
}
protected static class NullProto extends AbstractObj {
public static final int OBJECT_ID = ProtoRegistry.generateObjectID();
protected static final NativeCall nativeIdentical =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
NullImpl thiz = ensureType(NullImpl.class, context);
return thiz.getClass() == args[0].getClass()
? engine.getObjTrue()
: engine.getObjFalse();
}
};
protected static final NativeCall nativeNotIdentical =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
NullImpl thiz = ensureType(NullImpl.class, context);
return thiz.getClass() != args[0].getClass()
? engine.getObjTrue()
: engine.getObjFalse();
}
};
protected static final NativeCall nativeType =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
JClass typeHint = ensureType(JClass.class, args[0]);
return new NullImpl(typeHint.clazz);
}
};
protected static final NativeCall nativeAnd =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
return engine.getObjFalse();
}
};
protected static final NativeCall nativeOr =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
Clos closure = ensureType(Clos.class, args[0]);
engine.trigger(closure);
return null;
}
};
protected static final NativeCall nativeNot =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
return engine.getObjTrue();
}
};
private NullProto() {
slots.put(Str.SYM__id, nativeIdentical);
slots.put(Str.SYM__eq, nativeIdentical);
slots.put(Str.SYM__ni, nativeNotIdentical);
slots.put(Str.SYM__ne, nativeNotIdentical);
slots.put(Str.SYM__logic_and, nativeAnd);
slots.put(Str.SYM__logic_or, nativeOr);
slots.put(Str.SYM__logic_not, nativeNot);
slots.put(Str.SYM_not, nativeNot);
slots.put(Str.SYM_type, nativeType);
}
@Override
public int getObjectID() {
return OBJECT_ID;
}
public static void registerInContext(Context ctx) {
Base.registerInContext(ctx);
ctx.registerProto(OBJECT_ID, Base.OBJECT_ID);
ctx.registerObject(new NullProto());
}
}
}
protected static class NullProto extends AbstractObj {
public static final int OBJECT_ID = ProtoRegistry.generateObjectID();
protected static final NativeCall nativeIdentical =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
NullImpl thiz = ensureType(NullImpl.class, context);
return thiz.getClass() == args[0].getClass()
? engine.getObjTrue()
: engine.getObjFalse();
}
};
protected static final NativeCall nativeNotIdentical =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
NullImpl thiz = ensureType(NullImpl.class, context);
return thiz.getClass() != args[0].getClass()
? engine.getObjTrue()
: engine.getObjFalse();
}
};
protected static final NativeCall nativeType =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
JClass typeHint = ensureType(JClass.class, args[0]);
return new NullImpl(typeHint.clazz);
}
};
protected static final NativeCall nativeAnd =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
return engine.getObjFalse();
}
};
protected static final NativeCall nativeOr =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
Clos closure = ensureType(Clos.class, args[0]);
engine.trigger(closure);
return null;
}
};
protected static final NativeCall nativeNot =
new NativeCall() {
public Obj call(Engine engine, Obj context, Obj... args)
throws ClosureTerminatedException {
return engine.getObjTrue();
}
};
private NullProto() {
slots.put(Str.SYM__id, nativeIdentical);
slots.put(Str.SYM__eq, nativeIdentical);
slots.put(Str.SYM__ni, nativeNotIdentical);
slots.put(Str.SYM__ne, nativeNotIdentical);
slots.put(Str.SYM__logic_and, nativeAnd);
slots.put(Str.SYM__logic_or, nativeOr);
slots.put(Str.SYM__logic_not, nativeNot);
slots.put(Str.SYM_not, nativeNot);
slots.put(Str.SYM_type, nativeType);
}
@Override
public int getObjectID() {
return OBJECT_ID;
}
public static void registerInContext(Context ctx) {
Base.registerInContext(ctx);
ctx.registerProto(OBJECT_ID, Base.OBJECT_ID);
ctx.registerObject(new NullProto());
}
}
