} 第二种方式违反了命令-查询分离原则command-query separation principle。CQS是针对方法的经典oo设计原则,该原则指出,任何方法都可能是如下情况之一; 1.执行动作(更新,调整。。。)的命令方法,这种方法通常具有改变对象状态等副作用。并且是void的,没有返回值。 2向调用者返回数据的查询,这种方法没有副作用,不会永...
命令查询分离原则Command-query separation principle 在UML和模式应用一书中,发送给Die的roll消息之后跟随着第二个消息getFaceValue用于提取其新的faceValue,特别是:roll()方法是void的,没有返回值,例如: public void roll() { faceValue=//生成随机数 } public int getFaceValue() { return faceValue; } 为什...
Command-query separation (or CQS for short) is a design principle devised by Bertrand Meyer. CQS states that every method should either be acommandthat performs an action (changes state), or aquerythat returns answer to the caller (without changing the state or causing side-effects), but not...
Command-QuerySeparation Principle: Queries must not modify the instance. WikiMatrix When no arguments are given, then thecommand queriesthe default server. WikiMatrix Thecommand-querydistinction is important to the Eiffel method. WikiMatrix The IDENTIFY DEVICEcommand queriesa particular register on the ...
Separation of concerns is the key motivation behind Bertrand Meyer's Command Query Separation Principle: "The really valuable idea in this principle is that it's extremely handy if you can clearly separate methods that change state from those that don't. This is because you can use queries in...
What’s important here isn’t the status code we use but the logical separation of work into a write phase and a query phase. As you’ll see, we can use the CQS principle to make our systems faster and more scalable, but first, let’s fix the CQS violation in our existing code....
Em 1988, Bertrand Meyer introduziu a ideia de Command Query Separation, ou CQS, em seu livro Object-Oriented Software Construction, a ser aplicado a softwares orientados a objetos. A ideia fundamental é que os métodos de um objeto devem ser divididos em duas categorias: mé...
To send a query, append a question mark to the command name or parameter. When the recorder receives a query, it returns the relevant setting as a character string in an appropriate syntax. Queries can be used on some of the available setting and operation commands. Command name? terminator...
Commands (ie. requests to change the state of an application) are handled differently than requests to query the state of an application. This is huge! This separation of responsibilities suddenly makes the domain model practical. Domain models are awesome for making sure that the applicat...
Separation of concerns is the key motivation behind Bertrand Meyer's Command Query Separation Principle: "The really valuable idea in this principle is that it's extremely handy if you can clearly separate methods that change state from those that don't. This is because you can use queries in...