On 04.01.2020, at 16:03, Thiede, Christoph Christoph.Thiede@student.hpi.uni-potsdam.de wrote:
Hi Levente,
yes, that would look more intuitive for me. Why else should any of these methods ask for #allInstVarNames?
I would like to propose something like this:
copyFrom: anotherObject "Copy to myself all instance variables I have in common with anotherObject. This is dangerous because it ignores an object's control over its own inst vars. "
| otherInstVars | <primitive: 168> otherInstVars := (anotherObject class allInstVarNames withIndexCollect: [:name :index | name -> (anotherObject instVarAt: index)]) as: Dictionary. self class allInstVarNames withIndexDo: [:name :index | otherInstVars at: name ifPresent: [:value | self instVarAt: index put: value]]. (self class isVariable and: [anotherObject class isVariable]) ifTrue: [ 1 to: (self basicSize min: anotherObject basicSize) do: [:ind | self basicAt: ind put: (anotherObject basicAt: ind)]].
Well, that won't work with the primitive, right? -t
Best, Christoph
Von: Squeak-dev squeak-dev-bounces@lists.squeakfoundation.org im Auftrag von Levente Uzonyi leves@caesar.elte.hu Gesendet: Samstag, 4. Januar 2020 04:34 Uhr An: The general-purpose Squeak developers list Betreff: Re: [squeak-dev] Object >> #copyFrom: vs Object >> #copySameFrom:
Hi Christoph,
On Sat, 4 Jan 2020, Thiede, Christoph wrote:
Hi Levente, thanks for the feedback.
What's your use-case?
Actually not a real use case, I was just confused by the confusion of both methods.
But I would find it cool if my first code example would work, for the best support of converting arbitrary objects between each other.
It's not clear to me what the expected result of your first example is. Is it that instance variables are copied by name?
Levente
Best, Christoph
Von: Squeak-dev squeak-dev-bounces@lists.squeakfoundation.org im Auftrag von Levente Uzonyi leves@caesar.elte.hu Gesendet: Freitag, 3. Januar 2020 23:14:07 An: The general-purpose Squeak developers list Betreff: Re: [squeak-dev] Object >> #copyFrom: vs Object >> #copySameFrom: Hi Christoph,
On Fri, 3 Jan 2020, Thiede, Christoph wrote:
Hi Levente,
I don't get that.
Did I interpret your explanation correctly?
Yes, you did. I just checked why it doesn't work, and it turned out I misremembered how it actually works. The primitive's comment is:
Copy the state of the receiver from the argument. Fail if receiver and argument are of a different class. Fail if the receiver or argument are contexts (because of context-to-stack mapping). Fail if receiver and argument have different lengths (for indexable objects). Fail if the objects are not in a fit state to be copied (e.g. married contexts and Cogged methods
So, it'll fail, because the classes are not the same (an artifical limitation IMO). The fallback code will only copy slots of the same index if they have the same name (also an artificial limitation).
What's your use-case?
Levente
fooClass := Object newUniqueClassInstVars: 'a b' classInstVars: ''.
barClass := Object newUniqueClassInstVars: 'b c' classInstVars: ''. foo := fooClass new. bar := barClass new instVarNamed: #b put: 2; instVarNamed: #c put: 3; yourself. foo copyFrom: bar. foo instVarNamed: #b "expected: 2, actual: nil"
Otherwise, if I put #b as the first instvar in both classes, #copyFrom: and #copySameFrom: won't differ again ...
Best,
Christoph
_
Von: Squeak-dev squeak-dev-bounces@lists.squeakfoundation.org im Auftrag von Levente Uzonyi leves@caesar.elte.hu Gesendet: Freitag, 3. Januar 2020 19:05 Uhr An: The general-purpose Squeak developers list Betreff: Re: [squeak-dev] Object >> #copyFrom: vs Object >> #copySameFrom: Hi Christoph,
The two methods are different. #copyFrom: copies variables by index while #copySameFrom: copies variables by name. So, if you have an object named foo of class Foo with 2 instance variables a and b, and an object named bar of class Bar with 2 instance variables b and c, then foo copyFrom: bar will copy bar's b to foo's a, and bar's c to foo's b. #copySameFrom: will copy bar's b to foo's b and leave foo's a as is.
Levente
On Fri, 3 Jan 2020, Thiede, Christoph wrote:
Hi all,
I don't get the actual difference between #copyFrom: and #copySameFrom:.
The latter looks more "modern" to me, as it uses a primitive and has several implementors.
In my opinion, none of them actually matches its description ("Copy to myself all instance variables [named the same in | I have in common with] otherObject"). The following leaves o2 empty:
c1 := Object newUniqueClassInstVars: 'foo bar' classInstVars: ''. c2 := Object newUniqueClassInstVars: 'bar foo' classInstVars: ''. o1 := c1 new instVarNamed: #foo put: 6; instVarNamed: #bar put: 7. o2 := o1 as: c2. o2 instVarAt: 1 "nil".
o2 copySameFrom: o1. o2 instVarAt: 1 "nil".
Question: Could we deprecate #copySameFrom:, and in #copyFrom:, copy *all* matching instvars without respecting their order? Or did I miss any intended difference in behavior?
Best, Christoph