Class Definition Creation

To create a class in Salesforce:
  1. From Setup, click Develop | Apex Classes.
  2. Click New.
  3. Click Version Settings to specify the version of Apex and the API used with this class. If your organization has installed managed packages from the AppExchange, you can also specify which version of each managed package to use with this class. Use the default values for all versions. This associates the class with the most recent version of Apex and the API, as well as each managed package. You can specify an older version of a managed package if you want to access components or functionality that differs from the most recent package version. You can specify an older version of Apex and the API to maintain specific behavior.
  4. In the class editor, enter the Apex code for the class. A single class can be up to 1 million characters in length, not including comments, test methods, or classes defined using @isTest.
  5. Click Save to save your changes and return to the class detail screen, or click Quick Save to save your changes and continue editing your class. Your Apex class must compile correctly before you can save your class.

Classes can also be automatically generated from a WSDL by clicking Generate from WSDL. See SOAP Services: Defining a Class from a WSDL Document.

Once saved, classes can be invoked through class methods or variables by other Apex code, such as a trigger.

Note
To aid backwards-compatibility, classes are stored with the version settings for a specified version of Apex and the API. If the Apex class references components, such as a custom object, in installed managed packages, the version settings for each managed package referenced by the class is saved too. Additionally, classes are stored with an isValid flag that is set to true as long as dependent metadata has not changed since the class was last compiled. If any changes are made to object names or fields that are used in the class, including superficial changes such as edits to an object or field description, or if changes are made to a class that calls this class, the isValid flag is set to false. When a trigger or Web service call invokes the class, the code is recompiled and the user is notified if there are any errors. If there are no errors, the isValid flag is reset to true.

The Apex Class Editor

When editing Visualforce or Apex, either in the Visualforce development mode footer or from Setup, an editor is available with the following functionality:
Syntax highlighting
The editor automatically applies syntax highlighting for keywords and all functions and operators.
Search (Search icon)
Search enables you to search for text within the current page, class, or trigger. To use search, enter a string in the Search textbox and click Find Next.
  • To replace a found search string with another string, enter the new string in the Replace textbox and click replace to replace just that instance, or Replace All to replace that instance and all other instances of the search string that occur in the page, class, or trigger.
  • To make the search operation case sensitive, select the Match Case option.
  • To use a regular expression as your search string, select the Regular Expressions option. The regular expressions follow JavaScript's regular expression rules. A search using regular expressions can find strings that wrap over more than one line.

    If you use the replace operation with a string found by a regular expression, the replace operation can also bind regular expression group variables ($1, $2, and so on) from the found search string. For example, to replace an <h1> tag with an <h2> tag and keep all the attributes on the original <h1> intact, search for <h1(\s+)(.*)> and replace it with <h2$1$2>.

Go to line (Go To Line icon)
This button allows you to highlight a specified line number. If the line is not currently visible, the editor scrolls to that line.
Undo (Undo icon) and Redo (Redo icon)
Use undo to reverse an editing action and redo to recreate an editing action that was undone.
Font size
Select a font size from the drop-down list to control the size of the characters displayed in the editor.
Line and column position
The line and column position of the cursor is displayed in the status bar at the bottom of the editor. This can be used with go to line (Go To Line icon) to quickly navigate through the editor.
Line and character count
The total number of lines and characters is displayed in the status bar at the bottom of the editor.
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