Re: Beginners Digest, Vol 93, Issue 1: object instance browser

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Today's Topics:

  1. Re: object instance browser? (Herbert K?nig)
  2. Re: object instance browser? (Chris Muller)
  3. Re: object instance browser? (karl ramberg)


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Message: 1
Date: Tue, 31 Dec 2013 14:50:55 +0100
From: Herbert K?nig <[hidden email]>
Subject: Re: [Newbies] object instance browser?
To: [hidden email]
Message-ID: <[hidden email]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Merci vielmals.

Am 31.12.2013 11:27, schrieb Bert Freudenberg:

Yes, multiple ones in fact. This is a major reason working in

Smalltalk feels more immediate than in other environments.

......
Great explanation scrubbed


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Message: 2
Date: Tue, 31 Dec 2013 13:02:51 -0600
From: Chris Muller <[hidden email]>
Subject: Re: [Newbies] object instance browser?
To: "A friendly place to get answers to even the most basic questions
about Squeak." <[hidden email]>
Message-ID:
<CANzdToH+hPyJqeBqSdWLwROi5w_SbdAu_G9oWm3BgRkTqa=[hidden email]>
Content-Type: text/plain; charset=UTF-8

Great post, I learned some new things.

On Tue, Dec 31, 2013 at 4:27 AM, Bert Freudenberg <[hidden email]> wrote:

On 31.12.2013, at 08:53, David Holiday <[hidden email]> wrote:

Is there a way to browse the ecosystem of objects in a Smalltalk image?

Yes, multiple ones in fact. This is a major reason working in Smalltalk feels more immediate than in other environments.

I'm not talking about the class browser, what I'm looking for is a way to see what objects have actually been instantiated and what their state is.

The basic tool for this is called an Inspector. Whenever you have an expression, like "3 + 4", you press cmd-i to "inspect it", which opens an inspector on the result. This works in any text area. Try for example inspecting "self" in a class browser, and you will inspect the underlying class object (which the browser shows a high-level view of).

In the Inspector you see the objects referenced by this object (via instance variables or indexed fields) in the left panel. Select any of them and choose "inspect" from the context menu (or press cmd-i again). This way you can inspect all the objects in the system.

A more modern tool than the Inspector (which was around 40 years ago already) is the Object Explorer. It presents you a tree view of an object and its "children", which again are the instance variables and indexed fields of the object. Open it with cmd-shift-i (or "explore" in the context menu).

You can also do the reverse. If you choose "objects pointing to this value" you get an inspector showing all the objects that directly point to this object. Similarly there is a "reverse explorer", which you can open by selecting "explore pointers".

There are two roots to all the objects in the system:

       Smalltalk specialObjectsArray

which basically holds everything the Virtual Machine needs to know about, and in turn almost every object in the whole image, and

       thisContext

which is the current execution context, holding onto temporary objects. When a garbage collection is performed, any object not reachable form either of these two roots is removed from memory.

An "interesting" global object to explore is

       Project current

which holds your current workspace, in particular

       Project current world

, the root of all morphs in the world. And of course

       Smalltalk

itself is the dictionary that holds all global objects, including all classes (unless they are defined in a non-global environment).

There is also a low-level way to enumerate all objects in memory. "self someObject" will return the very first object in memory (which happens to be the nil object), and "anObject nextObject" will return the next one:

       | object count |

       count := 0.

       object := self someObject.

       [0 == object]

               whileFalse: [count := count + 1.

                       object := object nextObject].

       count

Interestingly, this also finds objects that are due to be garbage-collected. For example, if you accidentally closed a text window, there is a good chance its contents will still be in memory, and can be retrieved using an expression like

       ByteString allInstances last: 10

This makes use of the someInstance/nextInstance methods, which are similar to someObject/nextObject, but restricted to instances of one class only.

Hope you have fun poking around in the world of objects :)

- Bert -

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------------------------------

Message: 3
Date: Wed, 1 Jan 2014 02:23:04 +0100
From: karl ramberg <[hidden email]>
Subject: Re: [Newbies] object instance browser?
To: "A friendly place to get answers to even the most basic questions
about Squeak." <[hidden email]>
Cc: David Holiday <[hidden email]>
Message-ID:
<[hidden email]>
Content-Type: text/plain; charset="iso-8859-1"

I do it :-)

Happy new year!

Cheers,
Karl


On Tue, Dec 31, 2013 at 12:40 PM, Bert Freudenberg <[hidden email]>wrote:

Hey, I wrote it, you make the workspace, deal? ;)

Happy New Year, btw.

- Bert -

On 31.12.2013, at 12:37, karl ramberg <[hidden email]> wrote:

Make a Welcome Workspace with this info :-)

Cheers,

Karl

On Tue, Dec 31, 2013 at 11:27 AM, Bert Freudenberg <[hidden email]>wrote:

On 31.12.2013, at 08:53, David Holiday <[hidden email]> wrote:

Is there a way to browse the ecosystem of objects in a Smalltalk image?

Yes, multiple ones in fact. This is a major reason working in Smalltalk

feels more immediate than in other environments.

I'm not talking about the class browser, what I'm looking for is a way

to see what objects have actually been instantiated and what their state is.

The basic tool for this is called an Inspector. Whenever you have an

expression, like "3 + 4", you press cmd-i to "inspect it", which opens an

inspector on the result. This works in any text area. Try for example

inspecting "self" in a class browser, and you will inspect the underlying

class object (which the browser shows a high-level view of).

In the Inspector you see the objects referenced by this object (via

instance variables or indexed fields) in the left panel. Select any of them

and choose "inspect" from the context menu (or press cmd-i again). This way

you can inspect all the objects in the system.

A more modern tool than the Inspector (which was around 40 years ago

already) is the Object Explorer. It presents you a tree view of an object

and its "children", which again are the instance variables and indexed

fields of the object. Open it with cmd-shift-i (or "explore" in the context

menu).

You can also do the reverse. If you choose "objects pointing to this

value" you get an inspector showing all the objects that directly point to

this object. Similarly there is a "reverse explorer", which you can open by

selecting "explore pointers".

There are two roots to all the objects in the system:

       Smalltalk specialObjectsArray

which basically holds everything the Virtual Machine needs to know about,

and in turn almost every object in the whole image, and

       thisContext

which is the current execution context, holding onto temporary objects.

When a garbage collection is performed, any object not reachable form

either of these two roots is removed from memory.

An "interesting" global object to explore is

       Project current

which holds your current workspace, in particular

       Project current world

, the root of all morphs in the world. And of course

       Smalltalk

itself is the dictionary that holds all global objects, including all

classes (unless they are defined in a non-global environment).

There is also a low-level way to enumerate all objects in memory. "self

someObject" will return the very first object in memory (which happens to

be the nil object), and "anObject nextObject" will return the next one:

       | object count |

       count := 0.

       object := self someObject.

       [0 == object]

               whileFalse: [count := count + 1.

                       object := object nextObject].

       count

Interestingly, this also finds objects that are due to be

garbage-collected. For example, if you accidentally closed a text window,

there is a good chance its contents will still be in memory, and can be

retrieved using an expression like

       ByteString allInstances last: 10

This makes use of the someInstance/nextInstance methods, which are

similar to someObject/nextObject, but restricted to instances of one class

only.

Hope you have fun poking around in the world of objects :)

- Bert -

_______________________________________________

Beginners mailing list

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http://lists.squeakfoundation.org/mailman/listinfo/beginners

_______________________________________________

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