×
Namespaces

Variants
Actions
(Difference between revisions)

Implementing a Singleton using Symbian CCoeStatic class

From Nokia Developer Wiki
Jump to: navigation, search
jaaura (Talk | contribs)
m
hamishwillee (Talk | contribs)
 
(9 intermediate revisions by 3 users not shown)
Line 1: Line 1:
== Overview ==
+
[[Category:Symbian C++]][[Category:Code Snippet]][[Category:Mobile Design Patterns]][[Category:S60 3rd Edition (initial release)]][[Category:S60 5th Edition]][[Category:Symbian^3]][[Category:General Programming]]
The singleton pattern is one of the best-known patterns in software engineering. Essentially, a singleton is a
+
{{Abstract|This article shows how to create a singleton using {{Icode|CCoeStatic}} that can be used in Symbian C++ application classes (only). }}
class which only allows a single instance of itself to be created, and usually gives simple access to that
+
instance.
+
  
== Using class CCoeStatic to implement a singleton class ==
+
{{ArticleMetaData <!-- v1.1 -->
 +
|sourcecode= <!-- Link to example source code e.g. [[Media:The Code Example ZIP.zip]] -->
 +
|installfile= <!-- Link to installation file (e.g. [[Media:The Installation File.sis]]) -->
 +
|devices= <!-- Devices tested against - e.g. ''devices=Nokia 6131 NFC, Nokia C7-00'') -->
 +
|sdk= <!-- SDK(s) built and tested against (e.g. [http://linktosdkdownload/ Qt SDK 1.1.4]) -->
 +
|platform= S60 3rd Edition and later
 +
|devicecompatability= <!-- Compatible devices e.g.: All* (must have internal GPS) -->
 +
|dependencies= <!-- Any other/external dependencies e.g.: Google Maps Api v1.0 -->
 +
|signing= Self-Signed
 +
|capabilities= None
 +
|keywords= CCoeStatic
 +
|id= <!-- Article Id (Knowledge base articles only) -->
 +
|language= <!-- Language category code for non-English topics - e.g. Lang-Chinese -->
 +
|translated-by= <!-- [[User:XXXX]] -->
 +
|translated-from-title= <!-- Title only -->
 +
|translated-from-id= <!-- Id of translated revision -->
 +
|review-by= <!-- After re-review: [[User:username]] -->
 +
|review-timestamp= <!-- After re-review: YYYYMMDD -->
 +
|update-by= <!-- After significant update: [[User:username]]-->
 +
|update-timestamp= <!-- After significant update: YYYYMMDD -->
 +
|creationdate= 20070523
 +
|author= [[User:Giridharn]]
 +
}}
 +
{{SeeAlso|
 +
* [[WSD and the Singleton Pattern]]
 +
* [[How to create singleton class in Symbian]]
 +
* [[Implementing a Singleton Class in Symbian OS]]
 +
}}
  
A simpler way of implementing singletons than using TLS is possible for those classes which use the
+
== Overview ==
CCoeEnv class. Since CCoeEnv is a part of the UI control framework, this concerns only applications, not
+
application engines.
+
This applies also to S60 3rd Edition and later editions.
+
  
Singleton implementation based on CCoeStatic
+
The singleton pattern is one of the best-known patterns in software engineering. Essentially, a singleton is a class which only allows a single instance of itself to be created, and usually gives simple access to that instance.
  
== CMySingleton.h ==
+
This article explains how to create a singleton that can be used in classes which use the {{Icode|CCoeEnv}} class. Since {{Icode|CCoeEnv}} is a part of the UI control framework, this approach is only available to applications (not their engines). The approach is simpler than using TLS.
 +
 
 +
== Source code ==
 +
 
 +
=== CMySingleton.h ===
  
 
<code cpp>
 
<code cpp>
Line 44: Line 70:
  
  
== CMySingleton.cpp ==
+
=== CMySingleton.cpp ===
  
 
<code cpp>
 
<code cpp>
 +
 +
static const TUid KUidMySingleton = { 0x100000E9 };
 +
 
// -------------------------------------------------------------------------
 
// -------------------------------------------------------------------------
 
// CMySingleton::CMySingleton
 
// CMySingleton::CMySingleton
Line 76: Line 105:
 
return instance;
 
return instance;
 
}
 
}
 
 
</code>
 
</code>
[[Category:Symbian C++]][[Category:symbian OS]][[Category:Code Examples]]
 

Latest revision as of 03:55, 30 May 2013

This article shows how to create a singleton using CCoeStatic that can be used in Symbian C++ application classes (only).

Article Metadata
Compatibility
Platform(s): S60 3rd Edition and later
Symbian^3
S60 5th Edition
S60 3rd Edition (initial release)
Platform Security
Signing Required: Self-Signed
Capabilities: None
Article
Keywords: CCoeStatic
Created: giridharn (23 May 2007)
Last edited: hamishwillee (30 May 2013)

Contents

[edit] Overview

The singleton pattern is one of the best-known patterns in software engineering. Essentially, a singleton is a class which only allows a single instance of itself to be created, and usually gives simple access to that instance.

This article explains how to create a singleton that can be used in classes which use the CCoeEnv class. Since CCoeEnv is a part of the UI control framework, this approach is only available to applications (not their engines). The approach is simpler than using TLS.

[edit] Source code

[edit] CMySingleton.h

/**
* Example implementation of a singleton class by means of inheriting
* from CCoeStatic.
*/

class CMySingleton : public CCoeStatic
{
public: // constructors and destructor
/**
* Returns an instance of this class. When called for the first
* time, a new instance is created and returned. After that,
* calling InstanceL returns the same instance that was created
* earlier.
*
* @return A pointer to a CMySingleton object
*/

static CMySingleton* InstanceL();
private: // constructor
/**
* Default constructor is private because we are using the
* singleton design pattern.
*/

CMySingleton();
...
};


[edit] CMySingleton.cpp

static const TUid KUidMySingleton = { 0x100000E9 };
 
// -------------------------------------------------------------------------
// CMySingleton::CMySingleton
// C++ default constructor. It is private because we are using the
// singleton design pattern.
// -------------------------------------------------------------------------
CMySingleton::CMySingleton()
: CCoeStatic( KUidMySingleton )
{
}
// -------------------------------------------------------------------------
// CMySingleton::InstanceL
// Returns an instance of this class. When called for the first time,
// a new instance is created and returned. After that, calling
// InstanceL returns the same instance that was created earlier.
// Note that the UID passed to CCoeEnv::Static needs to be unique.
// -------------------------------------------------------------------------
CMySingleton* CMySingleton::InstanceL()
{
CMySingleton* instance = static_cast<CMySingleton*>
( CCoeEnv::Static( KUidMySingleton ) );
if ( !instance )
{
instance = new ( ELeave ) CMySingleton;
CleanupStack::PushL( instance );
instance->ConstructL();
CleanupStack::Pop();
}
return instance;
}
This page was last modified on 30 May 2013, at 03:55.
198 page views in the last 30 days.

Was this page helpful?

Your feedback about this content is important. Let us know what you think.

 

Thank you!

We appreciate your feedback.

×