I think Mr Pugh’s version is held in high regard because it only performs the instantiation of the singleton when getInstance() is called i.e. not when the class (the class holding the getInstance method) is loaded. If your singleton construction does something costly then this may be an advantage for you. If you’re like the … Read more
As noted, using global variables is generally bad engineering practice, unless absolutely needed of course (mapping hardware for example, but that doesn’t happen THAT often). Stashing everything in a class is something you would do in a Java-like language, but in C++ you don’t have to, and in fact using namespaces here is a superior … Read more
Sure this sounds confusing and can be debated. However, from the best practices i can put some suggestions. Singleton is usually used to create a resource intensive and one timer initialisation for instance: a database connector, login handler and such. Utility class are classes that only have static functions and variables. It should not deal … Read more
There’s a static reference to a singleton, so it won’t be eligible for garbage collection until the classloader is eligible for garbage collection. You can’t force any object to be garbage collected; you can request that the garbage collector runs with System.gc() but it’s only a request. If you really want to make a “singleton” … Read more
First, you should generally use -fPIC flag when building shared libraries. Not using it “works” on 32-bit Linux, but would fail on 64-bit one with an error similar to: /usr/bin/ld: /tmp/ccUUrz9c.o: relocation R_X86_64_32 against `.rodata’ can not be used when making a shared object; recompile with -fPIC Second, your program will work as you expect … Read more
While it’s true that “you can write and run tests aside of the actual program execution so that you are free to affect the global state of the program and run some tear downs and initialization per each test function to get it to the same state for each test.”, it is tedious to do … Read more
Singleton singleton = Singleton.getInstance(); is the correct way. Make sure your getInstance() method is indeed static. Since your Singleton implementation is far from being safe – your object can be instantiated via reflection, you may want to create a singleton based on enum
If you have a singleton class and you run two webapps that use this class in Tomcat both webapps will get 2 different instances of this singleton in JVM running the Tomcat. But if your webapp will use a singleton from JRE or Tomcat shared libs, eg Runtime.getRuntime webapps will get the same instance of … Read more
A DB connection should not normally be a Singleton. Two reasons: many DB drivers are not thread safe. Using a singleton means that if you have many threads, they will all share the same connection. The singleton pattern does not give you thread saftey. It merely allows many threads to easily share a “global” instance. … Read more
You would make that a module-level variable. For example, // In foo.js define(function () { var theFoo = {}; return { getTheFoo: function () { return theFoo; } }; }); // In bar.js define([“./foo”], function (foo) { var theFoo = foo.getTheFoo(); // save in convenience variable return { setBarOnFoo: function () { theFoo.bar = “hello”; … Read more