[Newbies] Dismissing an object

Ben Coman btc at openInWorld.com
Thu Oct 3 08:54:06 UTC 2013

Hi Azka,

 Maybe this helps: http://wiki.squeak.org/squeak/1584

Azka Niazi wrote:
> When we create an instance of a class with the new method, it does not show up in the world unless we use the openInWorld method. 

The 'World' Morphic UI interface is only a part of the system.  There 
are many more classes dealing with non-UI facilities like file access, 
file access, process scheduling and collections.  Should 
"OrderedCollection new" somehow appear on the screen ?
The #new method deals with the generic activity of creating new 
instances only, not the additional function of asking a morph to display 
itself in the World.

> To make it disappear we tried dismiss me option from the halo menu. 

By saying "tried" you imply this action failed. What gives you this 

> Does the dismissed object remain created somewhere in the background or does it get completely deleted from the system. 
It depends on if anything besides the 'World' references the object. In 
particular, if you store the instance in a variable in Workspace, that 
will prevent it from being garbage collected. For example, copy the 
following to a Workspace the evaluate each line one at a time.

Smalltalk garbageCollect.    EllipseMorph allInstances inspect.  
"Observe no instances"
x := EllipseMorph new. "Creates a new instance"
EllipseMorph allInstances inspect.  "Observe one instance"
x openInWorld. "Displays the instance"
"Close the morph using the halos"
Smalltalk garbageCollect.    EllipseMorph allInstances inspect.    
"Observe instance remains"
x openInWorld.  "Re-displays same instance"
"Close the morph using the halos"
x := nil.   
Smalltalk garbageCollect.    EllipseMorph allInstances inspect. "Observe 
no instances"

> Also, we have to ask, does evaluating (meaning repeatedly using the do it option) for the code which looks like this:className newCreate multiple objects of the same class in the background, or does it override the previously created object?
> Azka 	

Multiple evaluations of "SomeClassName new" creates multiple independent 
instances of that class.

cheers -ben

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