How These Code Elements Work Together
It is useful to understand how InterSystems IRIS uses the code elements introduced in this page.
The reason that you can use a mix of ObjectScript, Python, InterSystems SQL, class definitions, macros, routines, and so on is that InterSystems IRIS does not directly use the code that you write. Instead, when you compile your code, the system generates lower-level code that it uses. This is OBJ code for ObjectScript, used by the ObjectScript engine, and PYC code for Python, used by the Python engine.
There are multiple steps. It is not necessary to know the steps in detail, but the following points are good to remember:
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The class compiler processes class definitions and ObjectScript code into INT code for all elements other than Python methods. Python code is processed into PY code.
In some cases, the compiler generates and saves additional classes, which you should not edit. This occurs, for example, when you compile classes that define web services and web clients.
The class compiler also generates the class descriptor for each class. The system code uses this at runtime.
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For ObjectScript code, a preprocessor (sometimes called the macro preprocessor or MPP) uses the include files and replaces the macros. It also handles the embedded SQL in routines.
These changes occur in a temporary work area, and your code is not changed.
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Additional compilers create INT code for routines.
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INT code and PY code are an intermediate layer in which access to data is handled via direct global access. This code is human-readable.
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INT code is used to generate OBJ code, and PY code is used to generate PYC code. The InterSystems IRIS virtual machine uses this code. Once you have compiled your code into OBJ and PYC code, the INT and PY routines are no longer necessary for code execution.
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After you compile your classes, you can put them into deployed mode. InterSystems IRIS has a utility that removes the class internals and the intermediate code for a given class; you can use this utility when you deploy your application.
If you examine the InterSystems IRIS system classes, you might find that some classes cannot be seen because they are in deployed mode.
Note:
All class definitions and routines are stored in the same InterSystems IRIS databases as the generated code. This fact makes the code easier to manage. InterSystems IRIS provides a robust set of source control hooks that InterSystems developers have used for many years. You can use these hooks as well.
