#Compiler

As a developer, you have probably spent at least some time writing repetetive code. You may have even found yourself wishing you could generate the code programmatically. If this sounds familiar, this article is for you!

We'll start with an example. Note: the following examples use the %DynamicObject interface, which requires Caché 2016.2 or later. If you are unfamiliar with this class, check out the documentation here: Using JSON in Caché. It's really cool!

##Example

You have a %Persistent class that you use to store data.

Class Queries in InterSystems IRIS (and Cache, Ensemble, HealthShare) is a useful tool that separates SQL queries from Object Script code. Basically, it works like this: suppose that you want to use the same SQL query with different arguments in several different places.In this case you can avoid code duplication by declaring the query body as a class query and then calling this query by name. This approach is also convenient for custom queries, in which the task of obtaining the next row is defined by a developer. Sounds interesting? Then read on!

In my previous article, we reviewed possible use-cases for macros, so let’s now proceed to a more comprehensive example of macros usability. In this article we will design and build a logging system.

Logging system

Logging system is a useful tool for monitoring the work of an application that saves a lot of time during debugging and monitoring. Our system would consist of two parts:

• Storage class (for log records)
• Set of macros that automatically add a new record to the log

1.Background

        1.1 I met a few project that their interface servers were crashed. Cutoms wanted resume server as fast as we can. their servers are running at lan,and they can't use git,there are some namesapce in the server running different service,and usualy there is only one server.

        1.2 In the message,it has property in typeof characterstream,as you know,the message search page doesn't support filtering with  property of characterstream,so it's so hard to find the messge you want.

        1.3 Other workmate may update the code on the server,and mybe their is something wrong.

2.

In this article I would like to tell you about macros in InterSystems Caché. A macro is a symbolic name that is replaced with a set of instructions during compilation. A macro can “unfold” in various instruction sets each time it is called, depending on the parameters passed to it and activated scenarios. This can be both static code and the result of ObjectScript execution. Let's take a look at how you can use them in your application.

This is a translation of the following article. Thanks @Evgeny Shvarov  for the help in translation.

Let's assume that you wrote a program that shows "Hello World!", for example:

  write "Hello, World!"

The program works and everyone is happy.

With time, however, your program becomes more complex, gets more features and you eventually need to show the same string in different languages. Moreover you don't know the number and names of these languages.

The spoiler below contains a description of how the task of multi-language localization is solved in Caché.

Here you have an easy way to write and execute COS code from your unix scripts. This way one does not need to write routines or even open Studio or Atelier. It can be an option for simple and small actions for instance things like installation tasks or compiling.

See sample bash script (compile.sh) to compile classes:

#!/bin/bash
#####################################################################
# Script to compile classes
# $1 = NAMESPACE
# $2 = ClassName
#
# For example:
# ./compile.sh "SAMPLES" "Sample.Person" 
#####################################################################
echo -n "username:"
read username
echo -n "password:"
read pwd

csession HSINSTANCE -U "$1" <<EOFF
$username
$pwd
set status = \$SYSTEM.OBJ.Compile("$2")
h
EOFF

In most cases, if one class depends on another, the class compiler will detect this and determine the correct compilation order. For example:

• Compiling a superclass triggers compilation of its subclasses.
• Compiling a custom datatype class triggers compilation of any classes with a property of that type.

Yet sometimes, a developer needs to specify compilation order. InterSystems class definitions contain two keywords for this, DependsOn and CompileAfter, that are very similar but not identical.

Greetings! This article describes yet another simple way of creating installers for the solutions based on InterSystems Caché. The topic covers applications, which can be installed or completely removed from Caché with one action only. If you are still documenting installation instructions that have more than one step to do to install your application — it’s high time you automated this process. 

The attached file contains an example of code generation using ObjectGenerators which builds a very simple homemade RuleEngine. 

Code generation is an excellent way of increasing performance moving run-time calculations to compile-time.

We could generate code creating routines or implemeting methods using ObjectGenerators. In this example we are using ObjectGenerators.

Update: Rule Engine is now on GitHub https://github.com/intersystems-ib/cache-iat-ruleengine

On the back of my recent post on writing bug-less code I wanted to raise a few suggestions (to ISC) that would help prevent certain types of bugs at compile time. I've probably missed a few, but these are the main ones in my mind. Please contribute more suggestions.

Btw, these also serve as potential gotchas for new COS developers.

I except that introducing these types of changes can cause legacy code problems. Particularly where developers do some interesting overloading of method arguments.

So another topic that has been of interest to a number of people since the beta was put up last week is in regard to Studio Hooks and Atelier. This requires a bit of background and then some discussion of how the architecture of Atelier necessitates some changes and then what our current thinking on the subject is.

Studio hooks were added to Cache over 10 years ago. They have two primary usages. The first is that on an appropriate action such as creating a new document, or compiling a document a callback is executed whose job is to interact with external source control systems.

When do implicit assumptions in code and arithmetic operators pose a real danger, and how can this danger be overcome?

Constantinople in the 5th century AD

(It was possible for people to build grandiose buildings and vehicles without the use of computers and robots 1,600 years ago.)

If you assign dimensionless numbers to physical parameters in your code, you risk misunderstandings and errors when calculating and converting between units of measurement.

Welcome to the next chapter of my CI/CD series, where we discuss possible approaches toward software development with InterSystems technologies and GitLab.

Today I want to share a few approaches that will decrease your compilation time (especially if you're doing incremental/diff compilation rather than a full build).

Compiler flags and qualifiers

Code load and compilation are affected by a variety of flags and qualifiers. If you write deployment scripts for InterSystems platforms, I highly recommend reading them at least once through.

The class %Compiler.UDL.TextServices arrived in 2015.1, bringing us methods for exporting a class in UDL format (i.e. looking just like we're used to seeing it in Studio), and importing a UDL format definition back into a namespace. Some source control tools including our Deltanji are now able to use UDL format, resulting in diffs that are easier to understand.

When dealing with a support issue of one of our Deltanji source control sites this week I learned that if you're using InterSystems versions earlier than 2018.1 on Unix-type platforms it's possible that a class you export in UDL format will subsequently fail to import. So I'm posting this information here in case it helps other folk.

If you're doing Zen development your classes are likely to contain ClientMethod definitions scripted in Javascript. Prior to 2018.1 the UDL import processor used by methods of %Compiler.UDL.