about propertyAt: and others

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

What is Cocoon?

Phil

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On Sat, Mar 18, 2017 at 1:18 PM, stepharong <[hidden email]> wrote:

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