The main difference between a Singleton and a Class with a bunch of Class methods is that the Singleton can preserve some kind of state. For example, an array of data or some boolean flags. By calling sharedInstance, you access to the one and only instance of this class, that is being kept alive(and the … Read more
Yes, you need to export mySingleton by assigning it to module.exports. You also have a syntax error in your code (one of your braces is in the wrong place). Fixing those two things, you get: var mySingleton = (function() { var instance; function init() { var privateRandomNumber = Math.random(); return { getRandomNumber : function() { … Read more
Question: “If any error occurs when running the getInstance() method … and I still want the getInstance() method return the right result. How to achieve this?” Short answer: you can’t guarantee it. There are a large number of conditions which can throw a Throwable There are 2 main types (subclasses) of Throwable : Exception and … Read more
This is the non-lazy method of implementing the Singleton pattern for languages that support it. It’s perfectly acceptable to do this, especially since it’s one of the ways of implementing a thread-safe Singleton. However, if your Singleton object is expensive (see lazy initialization) to create, then it might not be appropriate to create it in … Read more
Like many object-oriented languages, Ruby has separation between methods in the class context and those in the instance context: class Example def self.a_class_method “I’m a class method!” end def an_instance_method “I’m an instance method!” end end When calling them using their native context it works: Example.a_class_method Example.new.an_instance_method When calling them in the wrong context you … Read more
You’ve declared the function GetDBConnection() to return no arguments. func GetDBConnection() { You have to tell Go the type of the argument you intend to return: func GetDBConnection() *sqlx.DB { As for determining the type, I just went to look at the source code. You could also look at the documentation on godoc.org, which is … Read more
As far as I know, the book AntiPatterns by Brown et al, 1998 may have been the first to popularise the term. It defines an anti-pattern like this: “An AntiPattern is a literary form that describes a commonly occurring solution to a problem that generates decidedly negative consequences.” I think that it’s worthwhile to pay … Read more