Understanding Smalltalk Syntax: The Building Blocks

July 15, 2024

This lesson delves into the syntax of Smalltalk, explaining the fundamental building blocks such as classes, methods, and messages. Readers will gain a solid understanding of how Smalltalk code is structured and organized.

Classes in Smalltalk

In Smalltalk, everything is an object, and classes are the blueprints from which objects are created. Classes define the properties and behaviors of objects. Let’s look at an example of a simple class definition in Smalltalk:

Object subclass: #Person
    instanceVariableNames: 'name age'
    classVariableNames: ''
    poolDictionaries: ''
    category: 'Example'

In this example, we define a class named Person with instance variables name and age.

Methods in Smalltalk

Methods in Smalltalk define the behavior of objects. They are defined within classes and are used to perform actions or return values. Here’s an example of a method definition in Smalltalk:

Person>>setName: aName
    name := aName.

This method setName: sets the name instance variable of a Person object to the value passed as a parameter.

Messages in Smalltalk

In Smalltalk, objects communicate by sending messages to each other. Messages are used to invoke methods on objects. Here’s an example of sending a message in Smalltalk:

| person |
person := Person new.
person setName: 'Alice'.

In this example, we create a new Person object and send the setName: message to set the name of the person to ‘Alice’.

Understanding the syntax of Smalltalk is essential for writing clear and concise code. By grasping the concepts of classes, methods, and messages, readers can start building their own Smalltalk applications with confidence.