/// <summary>Resolve an attribute reference. It can be in three possible places:
///
/// 1. the attribute list for the current template
/// 2. if self is an embedded template, somebody invoked us possibly
/// with arguments--check the argument context
/// 3. if self is an embedded template, the attribute list for the enclosing
/// instance (recursively up the enclosing instance chain)
///
/// Attribute references are checked for validity. If an attribute has
/// a value, its validity was checked before template rendering.
/// If the attribute has no value, then we must check to ensure it is a
/// valid reference. Somebody could reference any random value like $xyz$;
/// formal arg checks before rendering cannot detect this--only the ref
/// can initiate a validity check. So, if no value, walk up the enclosed
/// template tree again, this time checking formal parameters not
/// attributes Map. The formal definition must exist even if no value.
///
/// To avoid infinite recursion in toString(), we have another condition
/// to check regarding attribute values. If your template has a formal
/// argument, foo, then foo will hide any value available from "above"
/// in order to prevent infinite recursion.
///
/// This method is not static so people can overrided functionality.
/// </summary>
public virtual Object get(StringTemplate self, String attribute)
{
//System.out.println("get("+self.getName()+", "+attribute+")");
if (self == null)
{
return null;
}
if (lintMode)
{
self.trackAttributeReference(attribute);
}
// is it here?
Object o = null;
if (self.attributes != null)
{
o = self.attributes[attribute];
}
// nope, check argument context in case embedded
if (o == null)
{
IDictionary argContext = self.getArgumentContext();
if (argContext != null)
{
o = argContext[attribute];
}
}
if (o == null && self.getFormalArgument(attribute) != null)
{
// if you've defined attribute as formal arg for this
// template and it has no value, do not look up the
// enclosing dynamic scopes. This avoids potential infinite
// recursion.
return null;
}
// not locally defined, check enclosingInstance if embedded
if (o == null && self.enclosingInstance != null)
{
/*
System.out.println("looking for "+getName()+"."+attribute+" in super="+
enclosingInstance.getName());
*/
Object valueFromEnclosing = get(self.enclosingInstance, attribute);
if (valueFromEnclosing == null)
{
checkNullAttributeAgainstFormalArguments(self, attribute);
}
o = valueFromEnclosing;
}
return o;
}
