Code locality in CXP pages

The cxc-builder transpiles the CXP page into PRG code. For this, the cxc-builder creates Xbase++ code for the HTML markup and merges the generated code with the code in the <%...%> code sections defined in the CXP page. By default, the resulting code is injected into the :render() method of the page class.

However, sometimes more complex code needs to be added to a CXP page. For this, code locality directives can be used to tell the cxc-builder where to place the Xbase++ code in your code sections. The following code is injected into the header of the resulting PRG file, allowing the developer to add functions/procedures/classes or statics to a CXP page.

<!DOCTYPE html> 
<html> 
<%#code locality="page-global"%> 
<% 
// This section is injected into the module header 
STATIC aData := { 3, 5, 7, 11 } 

FUNCTION MyHelper(cInput) 
 LOCAL cDate 
 cDate := SubStr( CMonth(Date()), 1, 3) + ". " 
 cDate += Str( Day(Date()) ,2)          + ", " 
 cDate += Str( Year(Date()) ,4) 
RETURN(cDate) 
%> 
<body> 
<p>Today is @(MyHelper())!</p> 
</body> 
</html>

To sum it up, using <%#code locality> directives the location of your Xbase++ code in the generated code can be controlled. This way, your CXP pages and related code can be organized in such a way that there is no chaotic mixup between code and markup. To learn more about the separation between view and logic, see the CXP helperschapter.

CXP comes with the following localities for your code: page-init, page-load, page-unload, page-global and finally, the default locality which is page-render. For a detailed explanation of the different code localities, see the #code directivein the Language Reference chapter.

The following are some best-practice rules related to code locality.

Use page-load for database connects, table USE and other operations related to acquiring external resources. In case you return .F. from code defined with page-load locality, the CXP page returns a server error 500 to the client.

Use page-global for helper functions, classes or static data. Always try to avoid writing logic code mixed with markup code in code sections. Instead, add a helper function to the page-global section or even define a class to encapsulate your logic. This way, your page markup is better readable.

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Code locality in CXP pages Foundation