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Merge pull request #17 from intersystems-ru/cheat-sheet
Merge initial state of COS cheatsheet
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‎CHEAT.md

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# Cheat sheet
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Some most encountered COS expressions
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## Object/SQL Basics
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| Action | Code |
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|----------------------------------------------|-----------------------------------------------------------------------------------|
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| Call a class method | `Do ##class(package.class).method(arguments)`<br>`Set variable = ##class(package.class).method(arguments)`<br>Note: place a . before each pass-by-reference argument |
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| Call an instance method | `Do object.method(arguments)`<br>`Set variable = object.method(arguments)`<br>Note: place a . before each pass-by-reference argument |
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| Create a new object | `Set object = ##class(package.class).%New()` |
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| Open an existing object | `Set object = ##class(package.class).%OpenId(id, concurrency, .status)` |
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| Save an object | `Set status = object.%Save()` |
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| Retrieve the ID of a saved object | `Set id = object.%Id()` |
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| Retrieve the OID of a saved object | `Set oid = object.%Oid()` |
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| Validate an object without saving | `Set status = object.%ValidateObject()` |
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| Validate a property without saving | `Set status = ##class(package.class).PropertyIsValid(object.Property)` |
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| Print status after error | `Do $system.Status.DisplayError(status)`<br>`Zwrite status` (v2012.2+) |
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| Obtain status details after error | `Do $system.Status.DecomposeStatus(status, .err)` |
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| Remove an object from process memory | `Set object = ""` |
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| Delete an existing object of a class | `Set status = ##class(package.class).%DeleteId(id)` |
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| Delete all saved objects of a class | `Do ##class(package.class).%DeleteExtent()`<br>`Do ##class(package.class).%KillExtent()` |
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| Reload properties of a saved object | `Do object.%Reload()` |
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| Clone an object | `Set clonedObject = object.%ConstructClone()` |
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| Write a property | `Write object.property` |
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| Set a property | `Set object.property = value` |
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| Set a serial (embedded) property | `Set object.property.embeddedProperty = value` |
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| Link two objects | `Set object1.referenceProperty = object2` |
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| Populate a class | `Do ##class(package.class).Populate(count, verbose)` |
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| Remove all objects in process memory | `Kill` |
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| List all objects in process memory | `Do $system.OBJ.ShowObjects()` |
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| Display all properties of an object | `Do $system.OBJ.Dump(object)`<br>`Zwrite object` (v2012.2+) |
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| Determine If variable is an object reference | `If $isobject(variable) ; 1=yes, 0=no` |
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| Find classname of an object | `Write $classname(oref)` |
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| Start the SQL shell | `Do $system.SQL.Shell()` |
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| Test a class query | `Do ##class(%ResultSet).RunQuery(class, query)` |
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## ObjectScript Commands
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| Command | Description |
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|-------------------------------|-------------------------------------------------------------------------------------|
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| `Write` | Display text strings, value of variable or expression. |
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| `Set` | Set value of variable. |
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| `Do` | Execute method, procedure, or routine. |
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| `Quit` or `Return` (v2013.1) | Terminate method, procedure, or routine. Optionally return value to calling method. |
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| `Halt` | Stop Caché process and close Terminal. |
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| `Kill` | Destroy variable(s). |
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| `If {} ElseIf {} Else {}` | Evaluate conditions and branch. |
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| `For {}`, `While {}`, `Do {} While` | Execute block of code repeatedly. |
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| `Try {} Catch {}`, `Throw` | Handle errors. |
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## ObjectScript Functions
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| Action | Code |
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|--------------------------------------------------|-------------------------------------------------------------|
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| Date conversion (external → internal) | `Set variable = $zdh("mm/dd/yyyy")` |
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| Date conversion (internal → external) | `Set variable = $zd(internalDate, format)` |
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| Time conversion (external → internal) | `Set variable = $zth("hh:mm:ss")` |
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| Time conversion (internal → external) | `Set variable = $zt(internalTime, format)' |
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| Display current internal date/time string | `Write $horolog` |
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| Display UTC date/time string | `Write $ztimestamp` |
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| Display length of a string | `Write $length(string)` |
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| Build a list | `Set listString = $listbuild(list items, separated by comma)` |
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| Retrieve an item from a list | `Set variable = $list(listString, position)` |
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| Display the length of a list | `Write $listlength(listString)` |
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| Display random integer from start to start+count | `Write $random(count) + start` |
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| Check if variable exists | `Write $data(variable)` |
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| Return value of variable, or "" If undefined | `Write $get(variable)` |
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## Collections
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| Action | Code |
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|--------------------------------------------------------------|--------------------------------------------------------------------------------------------------------|
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| Create a new standalone list<br>Work with a list property | `Set listObject=##class(%ListOfDataTypes).%New()`<br>Use methods below on a list collection property |
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| Insert an element at the end of a list | `Do listObject.Insert(value)`<br>`Do object.listProperty.Insert(value)` |
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| Insert an element into a list | `Do listObject.SetAt(value, position)`<br>`Do object.listProperty.SetAt(value, position)` |
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| Remove an element from a list | `Do listObject.RemoveAt(position)`<br>`Do object.listProperty.RemoveAt(position)` |
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| Display an element of a list | `Write listObject.GetAt(position)`<br>`Write object.listProperty.GetAt(position)` |
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| Display the size of a list | `Write listObject.Count()`<br>`Write object.listProperty.Count()` |
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| Clear all the elements of a list | `Do listObject.Clear()`<br>`Do object.listProperty.Clear()` |
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| Create a new standalone array<br>Work with an array property | `Set arrayObject=##class(%ArrayOfDataTypes).%New()`<br>Use methods below on an array collection property |
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| Insert an element into an array | `Do arrayObject.SetAt(value, key)`<br>`Do object.arrayProperty.SetAt(value, key)` |
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| Remove an element from an array | `Do arrayObject.RemoveAt(key)`<br>`Do object.arrayProperty.RemoveAt(key)` |
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| Display an element of an array | `Write arrayObject.GetAt(key)`<br>`Do object.arrayProperty.GetAt(key)` |
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| Display the size of an array | `Write arrayObject.Count()`<br>`Do object.arrayProperty.Count()` |
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| Clear all elements of an array | `Do arrayObject.Clear()`<br>`Do object.arrayProperty.Clear()` |
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## Relationships
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| Action | Code |
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|-----------------------------------------|------------------------------------------------------------------------------------------|
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| Parent-to-children object linking | `Do parentObject.childRefProperty.Insert(chilDobject)`<br>`Set chilDobject.parentRefProperty = parentObject` |
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| One-to-many object linking | `Do oneObject.manyRefProperty.Insert(manyObject)`<br>`Set manyObject.OneRefProperty = OneObject` |
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| Write a property of a child object | `Write parentObject.childRefProperty.GetAt(position).property` |
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| Write a property of a many object | `Write oneObject.manyRefProperty.GetAt(position).property` |
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| Display the count of child/many objects | `Write parentObject.childRefProperty.Count()`<br>`Write oneObject.manyRefProperty.Count()` |
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| Open a many/child object directly | `Set object = ##class(package.class).IDKEYOpen(parentID, childsub)` |
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| Retrieve the id of a child object | `Set status = ##class(package.class).IDKEYExists(parentID, childsub, .childID)` |
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| Clear the child/many objects | `Do parentObject.childRefProperty.Clear()<br>Do oneObject.manyRefProperty.Clear()` |
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## Streams
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| Action | Code |
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|-------------------------------------------|---------------------------------------------------------------------------------------|
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| Create a new stream | `Set streamObject=##class(%Stream.GlobalCharacter).%New()`<br>`Set streamObject=##class(%Stream.GlobalBinary).%New()`<br>Use methods below on a stream property |
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| Add text to a stream | `Do streamObject.Write(text)`<br>`Do object.streamProperty.Write(text)` |
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| Add a line of text to a stream | `Do streamObject.WriteLine(text)`<br>`Do object.streamProperty.WriteLine(text)` |
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| Read len characters of text from a stream | `Write streamObject.Read(len)`<br>`Write object.streamProperty.Read(len)` |
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| Read a line of text from a stream | `Write streamObject.ReadLine(len)`<br>`Write object.streamProperty.ReadLine(len)` |
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| Go to the beginning of a stream | `Do streamObject.Rewind()`<br>`Do object.streamProperty.Rewind()` |
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| Go to the end of a stream, for appending | `Do streamObject.MoveToEnd()`<br>`Do object.streamProperty.MoveToEnd()` |
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| Clear a stream | `Do streamObject.Clear()`<br>`Do object.streamProperty.Clear()` |
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| Display the length of a stream | `Write streamObject.Size`<br>`Write object.streamProperty.Size` |
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## Unit Testing Macros
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| Action | Code |
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|-----------------------------|--------------------------------------------------|
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| Assert equality | `Do $$$AssertEquals(value1, value2, message)` |
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| Assert inequality | `Do $$$AssertNotEquals(value1, value2, message)` |
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| Assert status is OK | `Do $$$AssertStatusOK(status, message)` |
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| Assert status isn't OK | `Do $$$AssertStatusNotOK(status, message)` |
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| Assert condition is true | `Do $$$AssertTrue(condition, message)` |
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| Assert condition isn't true | `Do $$$AssertNotTrue(condition, message)` |
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| Log message | `Do $$$LogMessage(message)` |
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## Other Macros
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| Action | Code |
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|----------------------------------|-------------------------------------------|
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| Return a good status | `Quit $$$OK` |
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| Return an error status | `Quit $$$ERROR($$$GeneralError, message)` |
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| Throw exception on error | `$$$ThrowOnError(status, code)` or `$$$TOE(status, code)` |
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| Check if status is good | `If $$$ISOK(status)` |
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| Check if status is an error | `If $$$ISERR(status)` |
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| Return a null object reference | `Quit $$$NULLOREF` |
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| Place a new line within a string | `Write string1_$$$NL_string2` |

‎README.md

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to continue use that same style, than introducing yet another one, which may be more recommended
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but which will be introducing some unnecessary inconsistency.
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## Cheat sheet
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For COS cheat sheet refer [here](CHEAT.md).
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## Mandatory part
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* Only "modern" syntax permitted, dotted syntax is not generally allowed (with few exceptions);

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