About Classes in EasyLanguage

An EasyLanguage class defines the structure for an object that can contain members such as properties, members, and events.  Much like a blueprint, a class describes the actions (behavior) an object can perform and the information (data) it can access.  

The following are some of the terms are commonly associated with classes:

  • Objects - Instances of a class that allow users to access the methods and properties defined by the class from which it is created.  Multiple instances of the same class may be declared and used in an EasyLanguage document.  
  • Properties - Members of a class that allow your code to read and/or write stored values.  Each instance of a class (object) shares the same property definitions but can have different property values specific to that object.  
  • Methods - Members of a class that perform specific actions (much like a function) within a class such as data retrieval and calculations.  Methods often accept parameters (input values).  They can return data of a specified type or can be void (not return a value).  See Method for a description of the EasyLanguage reserved word used to create a local method.
  • Constructors - Special methods that execute each time a new instance of a class (object) is created. Use constructors to initialize the state of your new object  See Class Declaration for a generic class declaration and initialization example.
  • Dot operator - The period symbol (.) to the right of an object name is used to refer to a child element of an object (such as a property or method). For instance, in the expression PositionProvider1.Count, the dot operator indicates that the term Count is referring to an element of the object named PositionProvider1 that returns the number of available market positions within object.
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Class Categories

Although each class has a unique set of properties and methods, it is useful to think of them belonging to broad categories so that you'll have a better idea of what similar classes are designed to do.  

  • Components - Classes that are designed to be added to an EasyLanguage document from the TradeStation Development Environment toolbox and will automatically generate protected code that contains objects whose properties and events can be managed using the Properties editor.  A number of components, such as Providers and OrderTickets, are found in the TSData namespace sections of the Dictionary.
  • Collections - Classes that allow you to create objects that represent of collection of values that can be stored and accessed using common programming models including dictionaries, stacks, queues, and vectors.
  • Enumerations - Classes that consist of a set of named constants called enumerators that typically allow you to evaluate a state or action associated with a property of another class.
  • Exceptions - Classes that are typically used to identify errors and will throw an exception if the condition is true. The Exception base class provide a common set of methods and properties that may be accessed for these exceptions
  • Support Classes - Classes that designed to be used by higher level classes (such as Components) and generally reside in the same namespace as the classes that reference them.
  • System Classes - Classes that provide a general framework for other classes and typical reside under the ELSystem library.