I have ^self in my image but anyway, by default, if there is ^ in a method, it returns self... so an empty method (message) actually return self...

Cédrick

2006/8/31, Bakki Kudva bakki.kudva@gmail.com:

Hi,

I'm a bit confused about y ourself. I understand that the definition of yourself is ^self But when I browse Object and look at yourself: all I find is the description string.. "Answer self."

What happened to ^self? Where is the actual code implementing this?

Thanks,

bakki _______________________________________________ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners

On 31.08.2006, at 17:35, Bakki Kudva wrote:

Hi,

I'm a bit confused about y ourself. I understand that the definition of yourself is ^self But when I browse Object and look at yourself: all I find is the description string.. "Answer self."

What happened to ^self? Where is the actual code implementing this?

self is the default return value. So if you return nothing special, the compiler will add a ^self at the end.

A good rule is to make the ^self explicit as soon as it is important, thus for our lecture (#yourself is covered in 04: http://www.iam.unibe.ch/~scg/Teaching/Smalltalk/Slides/04Idioms.pdf )

we changed the implementation of #yourself to be

yourself "Answer self." ^self

This is in 3.9

Marcus

Hi Bakki,

yourself is used quite often for chaining messages. Long chains are definitely bad form but in some cases you are stuck without having yourself.

Take for example

aCollection add: 'hello'

When you first encounter this message many people make the mistake of believing that add: returns a collection. You will see bugs created in this way. For example someone might write

"THIS CODE DOES NOT WORK" aCollection := aCollection add: 'hello'.

Since after running this code what you get is aCollection = 'hello'. (Forget that the assignment isn't even necessary for the moment since aCollection is changed with add, you will still see this).

The result is not what you would expect.

To fix this you do:

"THIS CODE DOES WORK" aCollection := aCollection add: 'hello'; yourself.

This basically returns the "self" of the previous message instead of the value that is returned from the previous message.

Also consider this

MyClass class > createFrom: anOtherObject "return to the sender an instance of the receiver setting anOtherObject to someOtherObject" ^(MyClass new) someOtherObject: anOtherObject

if the mutator returns self you are ok if not this will not work. It usually does, but other methods may not for example:

MyClass class > createFrom: anOtherObject "return to the sender a processed instance of the receiver setting anOtherObject to someOtherObject" ^(MyClass new) someOtherObject: anOtherObject; processResult

if processResult sets a value on the object and returns the result then you are stuck. Fix it with yourself.

MyClass class > createFrom: anOtherObject "return to the sender a processed instance of the receiver setting anOtherObject to someOtherObject" ^(MyClass new) someOtherObject: anOtherObject; processResult; yourself.

Hope that helps!

Happy Coding

Ron Teitelbaum President / Principal Software Engineer US Medical Record Specialists Ron@USMedRec.com

-----Original Message----- From: beginners-bounces@lists.squeakfoundation.org [mailto:beginners- bounces@lists.squeakfoundation.org] On Behalf Of Bakki Kudva Sent: Thursday, August 31, 2006 11:36 AM To: A friendly place to get answers to even the most basic questions aboutSqueak. Subject: [Newbies] yourself

Hi,

I'm a bit confused about y ourself. I understand that the definition of yourself is ^self But when I browse Object and look at yourself: all I find is the description string.. "Answer self."

What happened to ^self? Where is the actual code implementing this?

Thanks,

bakki _______________________________________________ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners