Hi
I'm looking at cocoon and other property systems. I would like to get a
nice library once for all.
I want to also revisit Artefact stylesheets.
I'm checking the semantics regarding the lookup of a property in a parent
when it is not found in the receiver.
I have the impression that when there is a parent access and modification
should modify the same object: i.e., the parent if the key is found in the
parent or the child if the property is found in the child.
in cocoon we have a mix of the two semantics and I would like to get your
feel about it.
propertyAt: aKey
"Answer the value of the property ==aKey==, raises an error if the
property doesn't exist."
^ self propertyAt: aKey ifAbsent: [
self hasParent
ifTrue: [ self parent propertyAt: aKey ]
ifFalse: [self errorPropertyNotFound: aKey ]]
propertyAt: aKey default: aBlock
"Answer the value of ==aKey==. If the key have no entry I look on the
parent or execute a block if i'm an orphan."
^ self
propertyAt: aKey
ifAbsent: [
self hasParent
ifTrue: [ self parent propertyAt: aKey default:
aBlock ]
ifFalse: aBlock ]
but
propertyAt: aKey ifAbsent: aBlock
"Answer the value of the property ==aKey==, or the result of ==aBlock==
if the property doesn't exist."
^ self properties at: aKey ifAbsent: aBlock
propertyAt: aKey ifAbsentPut: aBlock
"Answer the value of the property ==aKey==, or if the property doesn't
exist adds and answers the result of evaluating ==aBlock==."
^ self properties at: aKey ifAbsentPut: aBlock
In PetitParser there is no lookup. But we can get back to this situation
by just not setting a parent.
My gut feeling is telling me that overriding on write is not really good
because
a client of the parent will not see the changes coming from a child.
I thaought that stylesheet was supporting lookup but it does not
testSubstyleAttributesOverride
styleSheet at: #textColor put: #red.
styleSheet > #sub > #subsub at: #textColor put: #blue.
self assert:( styleSheet get: #textColor ) equals: #red.
self assert:( styleSheet > #sub get: #textColor ) equals: #red.
self assert:( styleSheet > #sub > #subsub get: #textColor ) equals:
#blue.
Does not work
What you think?
Stef
