Checking if Directory or File Exists:

Outlined below is an example of how to check if a directory exists:

Set directoryName="c:\temp\nosuchdir"

/* Check for existence of a directory - Return Value:  0 - directory does not exist;  1 - directory does exist  */

Set directoryExists=##class(%File).DirectoryExists(directoryName)

If ('directoryExists)  // do the processing for when a directory does not exist


Outlined below is an example of how to check if a file exists:

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Article
· Sep 27, 2018 2m read
Method to Create a Class

The following class method "test" contains code that can create a new class, create new properties for classes, or create new methods for classes. "test" runs all three of these processes once, and the code that performs each action is labelled by comments in the method:


ClassMethod test() As %Status
{
    set sc = $$$OK
    
    // Create a class
    set class = ##class(%ClassDefinition).%New("MyClass")
    set class.Description = "This is my test class"_$c(13,10)_"testing %ClassDefinition"
    set class.Super = "%Persistent"

    // Create a property and add it
    set property = ##class(%PropertyDefinition).%New("MyClass.MyProperty")
    set property.Type = "%String"
    set property.Description="This is a property"
    set sc1 = class.Properties.Insert(property)
    do:$$$ISERR(sc1) $system.Status.DisplayError(sc1)
    set sc = $$$ADDSC(sc, sc1)
    
    // Create a method and add it
    set method = ##class(%MethodDefinition).%New("MyClass.MyMethod")
    set method.ReturnType = "%Integer"
    set method.FormalSpec = "x:%Integer,y:%Integer=10"
    set method.Description = "Return product of x and y"
    set method.CodeMode = "code"
    set method.Code = " new result"_$c(13,10)_" set result=x*y"_$c(13,10)_" quit result"
    set sc2 = class.Methods.Insert(method)
    do:$$$ISERR(sc2) $system.Status.DisplayError(sc2)
    set sc = $$$ADDSC(sc, sc2)
    
    // Save the class definition
    set sc3 = class.%Save()
    do:$$$ISERR(sc3) $system.Status.DisplayError(sc3)
    set sc = $$$ADDSC(sc, sc3)
    
    return sc
}

Here's a link to the code on GitHub

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An extension “extends” or enhances a FHIR resource or a data element in a custom way. The extension can be added to the root of a resource, such as “Patient.ethnicity” in US Core profile, and they can be added to individual elements such as HumanName, Address or Identifier.

Did you know that you can also add an extension to a primitive data type?

Primitives usually store a single item and are the most basic element in FHIR. For example: "Keren", false, 1234, 12/08/2024 etc.

For example, the patient resources might look like this:

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This code snippet provides a ZEN page that downloads a stream from its database directly:


/// We assume that you have stored your data within this schema:
/// MyApp.Model.Storage: Filename,FileSize,Content,ContentType
Class zen.downloadStream Extends (%ZEN.Component.page,%CSP.StreamServer)
{
 
    /// Wrapper to get the id of the download, we assume that the id is passed to this zen page
    /// as a URI parameter, i.e.: MyApp.Downloads.cls?OID=1234
    ClassMethod GetId()
    {
        Quit $Get(%request.Data("OID",1))
    }
     
    /// Set the appropriate header for the file.
    ClassMethod OnPreHTTP() As %Boolean
    {
        Set tId = ..GetId()
     
        If ##Class(MyApp.Model.Storage).%ExistsId(tId) {
            Set tStream = ##Class(MyApp.Model.Storage).%OpenId(tId)
            // You could "guess" the content type by its file extension
            // or you can store it (before) in the database separately (like in this example).
            // Set Extension = $Piece(tStream.Filename,".",$Length(tStream.Filename,"."))
            // Set ContentType = ..FileClassify(Extension)
     
            Set %response.ContentType = tStream.ContentType
            Do %response.SetHeader("content-disposition","attachment; filename="_tStream.Filename)
            Do %response.SetHeader("Content-Length",tStream.FileSize)
        }
        Else {
            Set %response.Status="404 File Not Found"
            Quit 0
        }
        Quit $$$OK
    }
     
    ClassMethod OnPage() As %Status
    {
        Set Download = ##Class(MyApp.Model.Storage).%OpenId(..GetId())
        Do Download.Content.OutputToDevice()
        Quit $$$OK
    }
 
}

Link to code on GitHub

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Article
· Aug 1, 2019 3m read
Nested set model for ObjectScript

In many projects I was faced with storing hierarchical data (tree) in classes.
By tree, I mean such data, where each node has a parent node — an object of the same class.
Many examples of such data can be given. For example, a catalog in the online store. Suppose that this online store sells books, in this case, the category tree might look like this:

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The attached code package provides a simple implementation of a web service client that utilizes the USPS Shipping API to normalize an address.

This code requires the developer to obtain a USPS Shipping API user ID which can be obtained from the USPS shipping API website. The assigned User Id can either be passed into the web service call as a parameter or can be coded as a parameter into the Request object.

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NOTE: This content was originally presented at the InterSystems Global Summit in 2014, however related topics often come up on the Developer Community so I have decided to turn this into an article for easier reference and discussion. However, much of the content was pulled directly from the presentation slides so the article format resembles that of a PPT deck more than paragraphs.

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Advent of Code is a series of 25 small programming challenges, it's an ideal way for beginners to start learning a computer language, and for advanced people to sharpen their programming skills.

There are small and bigger puzzles, which you can solve typically in half an hour to a few hours. (Looking at the leaderboard, the top aces can do them in less than 10 minutes.)

Advent of Code is created by Eric Wastl, you can find all info on https://adventofcode.com/.

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Advent of Code is a series of programming challenges for beginners and experienced Caché programmers.

For an introduction : look at article https://community.intersystems.com/post/advent-code-2016-day1-no-time-ta...

In this challenge, you need to find a password using instructions to move on a keypad.
Instructions can be U(p), D(own), L(eft) and R(ight).

You start at button 5 on a keypad like

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This is a series of programming challenges for beginners and experienced Caché programmers.

For an introduction : go to article https://community.intersystems.com/post/advent-code-2016-day1-no-time-ta...

You walk into a room, step on a tile and hear a loud click...

Traps !

The challenge is about avoiding traps.

You can recognise if a tile is a trap by following scheme :

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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

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This is a series of programming challenges for beginners and experienced Caché programmers.

For an introduction : go to article https://community.intersystems.com/post/advent-code-2016-day1-no-time-ta...

Today's challenge is a variation on the White Elephant gift exchange (https://en.wikipedia.org/wiki/White_elephant_gift_exchange), in this case, by a bunch of Elves where only one can have all gifts.

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The ideal number of table permissions to assign for your users is zero. Permissions should be granted upon sign-in based on the application used for access. For web applications, we have a simple way of doing this by appointing application roles, matching roles, and required resources in the System Management Portal.

ODBC and JDBC connections present a different problem, however, especially when third-party applications are involved. As providers of an ERP system, our customers often wish to be able to employ various software packages to integrate with or report on their data. Many of these programs are capable of running any kind of query. Yet, letting them do that can be devastating to a customer’s data.

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C:\data\backup.bat :

C:\InterSystems\Ensemble\bin\cache -s"C:\InterSystems\Ensemble\Mgr" -U%%SYS ##Class(Backup.General).ExternalFreeze() <C:\data\login.scr

echo %ERRORLEVEL%

rem note that we need to check errorlevel from highest to lowest here....

if errorlevel 5 goto OK

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Article
· Dec 27, 2018 2m read
Use %XML.Node to walk a DOM

The following code walks a DOM using %XML.Node. It also prevents %XML.Writer to change whitespace. Run the code using the class method "test":


Class objectscript.walkDOM Extends %Persistent
{
    ClassMethod dfs(node As %XML.Node)
    {
        s entrynode=node.NodeId
        do {
        //element nodes with one whitespacetyped child are the ones we want to change
        if (node.NodeType=$$$xmlELEMENTNODE){
            s snode=node.NodeId     
            if (node.MoveToFirstChild())            
                {
                    i ('node.MoveToNextSibling()){
                        i (node.NodeType=$$$xmlWHITESPACENODE){
                            s node.NodeType=$$$xmlTEXTNODE
                            s node.NodeId=snode
                        }
                    }
            }
            s node.NodeId=snode     
        }   
        if (node.HasChildNodes()){
            d node.MoveToFirstChild()
            d ..dfs(node)
        }
        } while (node.NodeType'="" && node.MoveToNextSibling())
        s node.NodeId=entrynode
         
    }
     
    ClassMethod test()
    {
      set xml = "abcdefg<![CDATA[   ]]>"
     
      s reader=##class(%XML.Reader).%New()
      do reader.OpenString(xml)  
      set writer = ##class(%XML.Writer).%New()
      //do some magic
      d ..dfs(reader.Document)
       
      w !,"with indent=1:",!
      set writer.Indent = 1
      do writer.OutputToString()
      do writer.Document(reader.Document)
      w writer.GetXMLString()
      set writer.Indent = 0
      w !,"with indent=0:",!
      do writer.OutputToString()
      do writer.Document(reader.Document)
      w writer.GetXMLString()
    }
}

Here's a link to the code on GitHub: https://github.com/intersystems-community/code-snippets/blob/master/src/...

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RESTful API Call From Cache to Particle.io Electron

Tom Fitzgibbon | Multidata | 212-967-6700 x537 | tom@mul.com

Summary: Simple Blink Tutorial for Particle.io Electron Device from Cache

Electron device is a tiny ARM processor ($40-$60) that connects to Particle’s world wide leased 2G/3G network (about $3/mo) and runs off an included LiPo battery. Using Cache’s %Net.HttpRequest you can send/receive data, control hardware and read sensors.

Step by Step (about 1 hour)

1) Get the Electron from store.particle.io.

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This is a series of programming challenges for beginners and experienced Caché programmers.

For an introduction : go to article https://community.intersystems.com/post/advent-code-2016-day1-no-time-ta...

The challenge of day 21 is about scrambling passwords.

There are a few functions you need to implement that will do operations on a string :

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This code snippet sends an XML request to a server and saves the response to a file. The class method "test" runs the code:


Class objectscript.postXML
{
    classmethod test() {
        Set HTTPRequest = ##class(%Net.HttpRequest).%New()
        Set HTTPRequest.ContentType = "text/xml"
        Set HTTPRequest.NoDefaultContentCharset = 1
        Set HTTPRequest.Location = "ITOMCZ"
        Set HTTPRequest.Server = "wph.foactive.com"
        Do HTTPRequest.RemoveHeader("User-Agent")  
        Do HTTPRequest.RemoveHeader("Accept-Encoding") 
        Do HTTPRequest.RemoveHeader("Connection")
        Do HTTPRequest.SetHeader("Expect","100-continue")
     
        Set RequestXML = ##class(%Library.File).%New("c:\test.xml")
        Do RequestXML.Open("RS")
        Do HTTPRequest.EntityBody.CopyFrom(RequestXML)
        Do RequestXML.%Close()
     
        Do HTTPRequest.Post(HTTPRequest.Location)
     
        Do $System.OBJ.Dump(HTTPRequest)
        Do $System.OBJ.Dump(HTTPRequest.HttpResponse)
     
        Write HTTPRequest.HttpResponse.Data.Size
        Write HTTPRequest.ContentLength
     
        Set ResponseStream = ##class(%Stream.FileBinary).%New()
        // Second part is typically the file extension, i.e.: application/pdf -> pdf
        Set FileType = $Piece(HTTPRequest.HttpResponse.GetHeader("CONTENT-TYPE"),"/",2)
        Set ResponseStream.Filename = "C:\test."_FileType
     
        Write ResponseStream.CopyFrom(HTTPRequest.HttpResponse.Data)
     
        Write ResponseStream.%Save()
        Do ResponseStream.%Close()
    }
}

Here's a link to the code on GitHub

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There have been a few use cases recently within InterSystems where we've needed to connect to Caché-based web services from PHP. The first of these was actually the Developer Community itself, which uses web services as part of Single Sign-On with other InterSystems sites/applications. The following example demonstrates how to connect to a Caché-based web service (particularly, the web service in the SAMPLES namespace) from PHP, using password authentication.

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Article
· Apr 25, 2024 3m read
Making A Variable Watch Itself

I came up with a challenge for myself to come up with a way to make a variable watch itself for a certain value and do something when it hits that value without having to check it every time something touches it. Basically, a way to say "if at any point during the execution of this code, if x = 0 (or whatever the condition is) do this thing." The class I ended up with watches a %Status:

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