Compiler

Syndicate content 5 

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. They are useful during development, and also when importing and compiling a set of classes for the first time.

The documentation for these keywords is here

Last comment 31 January 2019
+ 4   0 3
402

views

+ 4

rating

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.

Last comment 24 July 2017
+ 8   0 5
1032

views

+ 8

rating

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.

Last comment 20 May 2017
+ 8   0 1
322

views

+ 8

rating

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. Therefore I would see these as an option that would need to be enabled and that it won't prevent compilation (it would warn not error).

As an alternative I could see these being implemented as a Lint tool. This is something I (and perhaps the community) would be willing to do if we had an open source AST tree as a starting block (if anyone is aware of one in existence for COS)

Last comment 18 April 2017
+ 4   0 1
678

views

+ 4

rating

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

Last comment 24 March 2017
+ 6   1 8
891

views

+ 6

rating

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.

Last comment 1 February 2017
+ 1   0 1
139

views

+ 1

rating

Class Queries in InterSystems Caché is a useful tool that separates SQL queries from Caché 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!

Last comment 9 December 2016
+ 14   0 9
3697

views

+ 14

rating

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. Now, suppose that you are ingesting some data in JSON format, using the %DynamicObject interface. How do you map the %DynamicObject structure to your class? One solution is to simply write code to copy the values over directly

Last comment 22 November 2016
+ 15   0 7
1038

views

+ 15

rating

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

This is the output from the console

Last comment 14 October 2016
+ 4   0 3
458

views

+ 4

rating

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. 

Last comment 10 May 2016
+ 5   0 6
998

views

+ 5

rating

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. This is done by writing COS scripts that “do the right thing” for a given source control system based on the callback invoked. All of this code ran on the server and used all the facilities available on the server such as locks and transactions etc

Last comment 3 March 2016
+ 3   0 6
947

views

+ 3

rating

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

A very simple code generated method

For starters, let's begin with a very basic code generated method

+ 4   0 1
0

comments

348

views

+ 4

rating