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Catalog / Smalltalk Cheatsheet

Smalltalk Cheatsheet

A concise reference for Smalltalk syntax, core concepts, and common idioms, designed to assist both beginners and experienced developers.

Core Syntax & Concepts

Basic Syntax

Message Sending (Method Call)

receiver message
receiver message: argument
receiver message: arg1 message2: arg2

Assignment

variable := expression.

Blocks (Anonymous Functions)

[ expression. expression ]
[:arg1 :arg2 | expression]

Return

^ expression

Comments

"This is a comment"

Cascading

object message1; message2; message3.

Literals

Integers

123, -456

Floating-Point Numbers

3.14, -0.001

Characters

$a, $Z

Strings

'Hello, world!'

Symbols

#mySymbol, #+

Arrays

#(1 2 3), #( 'a' 'b' 'c' )

Keywords

true, false, nil

Control Structures

Conditional Statements

If True

condition ifTrue: [ expression ]

If False

condition ifFalse: [ expression ]

If True: Else:

condition ifTrue: [ trueExpression ] ifFalse: [ falseExpression ]

Boolean Logic

and:, or:, not (as a message to a boolean receiver)

Loops

While True

[ condition ] whileTrue: [ expression ]

While False

[ condition ] whileFalse: [ expression ]

Times Repeat

5 timesRepeat: [ expression ]

Integer to:do:

1 to: 10 do: [ :i | expression ]

Collection do:

#(1 2 3) do: [ :each | Transcript show: each printString ]

Collections

Common Collection Operations

Adding elements

collection add: element

Removing elements

collection remove: element

Checking for element existence

collection includes: element

Getting the size

collection size

Testing if empty

collection isEmpty

Iterating

collection do: [ :each | expression ]

Specific Collection Types

Arrays

Array new: 5. Array with: 1 with: 2 with: 3.

Dictionaries

Dictionary new. dictionary at: 'key' put: 'value'.

Sets

Set new. set add: 'element'.

Ordered Collections

OrderedCollection new. orderedCollection add: 'element'.

Classes and Objects

Defining a Class 

Object subclass: #MyClass
	instanceVariableNames: 'instanceVar1 instanceVar2'
	classVariableNames: ''
	poolDictionaries: ''
	category: 'MyCategory'

Instance variables are declared within the instanceVariableNames: field.

Methods

Instance Method Definition:

!MyClass methodsFor: 'accessing'!
myMethod
	^ instanceVar1
! !

Class Method Definition:

!MyClass class methodsFor: 'instance creation'!
new
	^ super new initialize
! !

Method categories help organize methods within a class definition.

Object Creation

MyClass new

Often, the initialize method is overridden to perform object setup.
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