[Newbies] Some general questions
Hello Is there a way to use a string as the name for a object? For example if I have the input string 'fred' from a user input field how do I create a object named userFred or even just fred? What is the difference between the source file and the image? Does the image use the code from the source file? If I create code dose it live in the image or source file? Is there a way to trigger a save prompt when clicking on the window close button? And a question about posting to this list: I notice that the replies to my last post didn't have 'Re' prefixed to them. How do I reply to a thread. For my lat post it seems that I accidentally relayed to the thread I had started by starting a new thread -oops. Darren ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Some general questions
On Tue, 2007-05-22 at 15:58 +0100, Darren White wrote: Hello Is there a way to use a string as the name for a object? For example if I have the input string 'fred' from a user input field how do I create a object named userFred or even just fred? You can get the class object from a String by using Smalltalk classNamed: #fred On this class you can invoke new to get an object. What is the difference between the source file and the image? Does the image use the code from the source file? If I create code dose it live in the image or source file? There are three files: sources, changes, image. The sources file never changes if you are working with the image. The changes file records all source code you enter/alter. The image contains all the compiled source code and the objects which have been created from there. The image is the actual state of your environment which have been dumped to disk. Is there a way to trigger a save prompt when clicking on the window close button? I don't know. Usually it is the other way round. You will be asked to close the window discarding unsaved changes. Norbert ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Some general questions
On Tuesday 22 May 2007 8:28 pm, Darren White wrote: Hello Is there a way to use a string as the name for a object? For example if I have the input string 'fred' from a user input field how do I create a object named userFred or even just fred? Use asSymbol to convert string to symbol and use it in subclass: method: BigBoss subclass: 'SmallBoss' asSymbol instanceVariableNames . What is the difference between the source file and the image? Does the image use the code from the source file? If I create code dose it live in the image or source file? The image is your Squeak computer. If you open the System Browser, the last button in the bottom frame of System Browser is set to 'show source'. If you change it to 'bytecodes' you will see instructions for methods. If you set it to 'decompile', then bytecodes are converted to Smalltalk code, but you wont see comments or descriptive parameter names. With 'show source', the browser will pull out readable text from the Sources files. Now if you are a programmer and make any changes to the displayed code, the changes are saved in 'changes' file. Open a 'simple change sorter' to browse through the changes. Now you can pick 'showDiffs' to see a pretty picture of what you have changed. Changes can be filed out into change sets. These change sets can be filed into another image. The Squeak team aggregates such changesets and merges them to produce the next version of the Image and Sources files. Squeak's smooth integration of toolchain makes it all appear so easy! Hope this helps .. Subbu ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
RE: [Newbies] Some general questions
Hi Darren, Chances are you don't want an object called UserFred. What you want instead is an object with an ivar #name that has the value 'Fred'. Unless Fred is a unique type of object User that can do things that all other Users can not or if Fred is not allowed to do some things that all other users are, you shouldn't think of subclasses as instances of objects. Instances are identified mostly by their content. So Object subclass: #User instanceVariableNames: 'userName' User class newForUserNamed: aUserName create an instance of User and assign aUserName to the userName instance variable ^self new userName: aUserName; yourself now you can go to a workspace and do this. User newForUserNamed: 'Fred'. If you highlight it and inspect it you will get back a user named 'Fred'. (User class means that the method that you write goes on the class you create called User on the class side [press the class button]) Happy coding! Ron Teitelbaum From: Darren White Hello Is there a way to use a string as the name for a object? For example if I have the input string 'fred' from a user input field how do I create a object named userFred or even just fred? What is the difference between the source file and the image? Does the image use the code from the source file? If I create code dose it live in the image or source file? Is there a way to trigger a save prompt when clicking on the window close button? And a question about posting to this list: I notice that the replies to my last post didn't have 'Re' prefixed to them. How do I reply to a thread. For my lat post it seems that I accidentally relayed to the thread I had started by starting a new thread -oops. Darren ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Some general questions
Hi! On Tuesday 22 May 2007 8:28 pm, Darren White wrote: Hello Is there a way to use a string as the name for a object? For example if I have the input string 'fred' from a user input field how do I create a object named userFred or even just fred? Use asSymbol to convert string to symbol and use it in subclass: method: BigBoss subclass: 'SmallBoss' asSymbol instanceVariableNames . Ehm... I am not sure Darren wanted to know how to programmatically create a new *class*. Darren - when you write an object named userFred what do you mean? Do you mean an object with an attribute (instance variable) holding a name? Normally you would create a class called say... User by editing the class template in the browser to look like this and then press alt-s: Object subclass: #User instanceVariableNames: 'name age' classVariableNames: '' poolDictionaries: '' category: 'MyClasses' Here you see that we defined two instance variables - name and age. The above would roughly translate to a table called User with two fields (columns), one called name and one called age - if you happen to be a database guy that might get you to understand this. Then if you add setter and getter methods to the class that look like: name: aString name := aString - name ^name -- ..and same for age - then you can do this: | freddie | - this is declaring a local variable, can be called whatever freddie := User new. freddie name: 'Fred'. freddie age: 12. freddie If you now select the above in a workspace and do inspect it, the code will be run, a new User object is created, we set its two instance variables and then the last line is just a reference to the object so that the inspector knows which object to inspect. Did this clear things up? What is the difference between the source file and the image? Does the image use the code from the source file? If I create code dose it live in the image or source file? A shorter answer here is that the sources file is never modified. We all have the same, it holds old source code and you need not worry about it - but you need it somewhere. :) The image file and the changes file is a pair that should never be separated. The changes file is an incremental log of all your source code modifications. Keep them together at all times. So your code lives in both the image (in compiled form) and in the changes file (in ascii form). regards, Göran ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] Re: Some general questions
Hello Darren, DW 10 timesRepeat: [ DW x := 1 asString. DW ''the value of x can be any string object DW userhow do I add x to be part off the name so I end up with DW variable named user1 user2 ... := User new. DW x := x + x.] if I don't misunderstand you, you want to put your users in a subclass of Collection, first guess is OrderedCollection. There is no need to have a single variable with a unique name for each user. So up to now I don't understand why the system should name the object. Is it a possibility to say: users := OrderedCollection new. Then a user enters his details in an instance of class User and you put it into the collection users by: newUser := User new. user name: to add the name to the new user users add: newUser. to stuff this user into the collection of users Collection and subclasses offer methods like: users select: [:eachUser | eachUser name = 'willi'] to give you a collection of all users named 'willi'. If this points in the right direction read up on collections and their enumeration methods. Else hope for someone to understand you better or clarify your intentions for me :-)) Cheers Herbertmailto:[EMAIL PROTECTED] ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
[Newbies] Re: Some general questions
Following Bert, the key used to access the dictionary could also be the
instance variable 'name' of the User.
So, if you now that names are unique, you can write:
users := Dictionary new.
names := #('Fred' 'Julia' 'Oliver' 'Martha').
names do: [:aName | | aUser |
aUser := User new.
aUser name: aName.
users at: aUser name put: aUser].
^users at: 'Fred'
Of course, if you further change the name of a user, users will get messy...
(users at: 'Fred') name: 'John'.
^users at: 'Fred'.
User 'John' is still registeered at key 'Fred'...
How to update the Dictionary would be another lesson.
If names are not unique, but you still want to access by name, no
problem, you can well make a Dictionary where each entry is a collection
of users sharing same name...
usersByName := Dictionary new.
names := #('Fred' 'Julia' 'Oliver' 'Martha' 'Fred').
names do: [:aName | | aUser |
aUser := User new.
aUser name: aName.
(usersByName at: aUser name ifAbsentPut: [OrderedCollection new])
add: aUser].
^usersByName at: 'Fred'
Then i guesse you will have a birthdate coupled to the name or other
kind of ID to differentiate your users...
After learning a bit of the Collection subclasses, you will see that you
can program as you think.
Nicolas
Bert Freudenberg a écrit :
On May 23, 2007, at 17:16 , Bert Freudenberg wrote:
On May 23, 2007, at 16:37 , Darren White wrote:
Hello, Thanks fro the replies.
I think my first question was a little fuzzy. I think what I need to
do as change the question.
If for example I have a seaside web app and users need to create an
account. Now, for each user I create an object, say an instance of
class Users, which has instance variables such as name and address.
So the new user puts in their detail such as name, address, telephone
number and then click register. How should (not what) the system name
this object. What I'm confused about is I don't know how may users
the system will have have do I name all the user object; I can't call
them all aUser . If the first user gets an object named user1 how do
I create another instance of User named user2 or What about If I want
to use one of the input field as part of the name of the object?
The example below may make it clear what I mean
10 timesRepeat: [
x := 1 asString.
''the value of x can be any string object
userhow do I add x to be part off the name so I end up with variable
named user1 user2 ... := User new.
x := x + x.]
There is a cool thing called a collection that can hold as many
users as you want:
users := OrderedCollection new.
10 timesRepeat: [users add: User new].
And later you can access an individual user like this:
users at: 2
users at: 5
Also, there is another kind of collection named dictionary that allows
to use objects other than integers (like strings) to be the key:
users := Dictionary new.
1 to: 10 do: [:i | users at: ('user', i asString) put: (User new)]
(I added parens for clarity, they're not necessary in this case)
Retrieval goes like this:
users at: 'user5'
Cheers,
- Bert -
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[Newbies] shortcut to search all categories for a particular class?
Hi all - is there an easy way to google Smalltalk, so to speak? If I know the class name but not its location in the System Browser, is there an easy shortcut which will take me directly to the code for the class? -- Giles Bowkett Blog: http://gilesbowkett.blogspot.com Portfolio: http://www.gilesgoatboy.org ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] shortcut to search all categories for a particular class?
On 5/23/07 10:57 PM, Giles Bowkett [EMAIL PROTECTED] wrote: Hi all - is there an easy way to google Smalltalk, so to speak? If I know the class name but not its location in the System Browser, is there an easy shortcut which will take me directly to the code for the class? If I understand, you want to find a class, because there is no Class Finder as their is a Method Finder. If that's the case then roll your mouse pointer over the class categories pane, the first pane in an open browser, and press Esc and then Return, and you'll get a window asking for the name of the class you want. Or put the mouse pointer in the same place, and press Command+f (on a Mac). Chris Cunnington ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
Re: [Newbies] shortcut to search all categories for a particular class?
On Thursday 24 May 2007 8:27 am, Giles Bowkett wrote: Hi all - is there an easy way to google Smalltalk, so to speak? If I know the class name but not its location in the System Browser, is there an easy shortcut which will take me directly to the code for the class? ALT+F with the cursor in the class category. Hope this helps .. Subbu ___ Beginners mailing list Beginners@lists.squeakfoundation.org http://lists.squeakfoundation.org/mailman/listinfo/beginners
