Grails域的類的語法解釋

Question

class User { 
    static constraints = { 
     password(unique:true, length:5..15, validator:{val, obj -> 
      if(val?.equalsIgnoreCase(obj.firstName)) { 
       return false 
      } 
     } 
    } 
} 

我發現這個groovy語法真令人費解。我花了幾天的時間來學習Grails/Groovy。我知道它做了什麼，但我並不真正瞭解它。

有人可以解釋這是如何工作的？

什麼是約束？它是一個關閉，密碼被稱爲一個函數？ 它是如何被調用的？

驗證程序怎麼樣的語法呢？

就像我說的，我可以看到它做了什麼，我只是不明白它是如何做到的。

Answer 1

前言 - 有些部分需要Groovy使用的基本知識。

//Domain Class 
class User { 
    //A property of the domain class 
    //corresponding to a column in the table User. 
    String password 

    //Domain classes and Command objects are treated specially in Grails 
    //where they have the flexibility of validating the properties 
    //based on the constraints levied on them. 
    //Similar functionality can be achieved by a POGO class 
    //if it uses @Validateable transformation at the class level. 
    static constraints = { 
     //Constraints is a closure where validation of domain class 
     //properties are set which can be validated against when the domain class 
     //is saved or validate() is called explicitly. 
     //This is driven by AbstractConstraint and Constraint java class 
     //from grails-core 

     //Constraint on password field is set below. 
     //Here password is not treated as a method call 
     //but used to set the parameter name in the constraint class on which 
     //validation will be applied against. Refer AbstractConstraint 
     //for the same. 
     password(unique:true, size:5..15, validator:{val, obj -> 
      //Each of the key in the above map represents a constraint class 
      //by itself 
      //For example: size > SizeConstraint; validator > ValidatorConstraint 
      if(val?.equalsIgnoreCase(obj.firstName)) { 
       return false 
      } 
     } 
    } 
} 

上面提到的是約束如何工作的基礎知識。如果您需要了解更多的詳細信息，然後這裏有一些你絕對需要的，如果你得到關於它的使用任何進一步的問題訪問來源：

• Constraints
• ConstrainedProperty
• Validation in Grails
• grails-core validation source code
• Search in Stackoverflow

鄂畢虛擬地說，如果你被困在與約束有關的任何實現中，SO是提問的好地方。隨意使用這個社區來幫助你克服有問題的程序化情況。

Answer 2

我有同樣的問題，也找不到Groovy書籍/文檔中解釋的語法。然後我谷歌和找到這個博客：http://www.artima.com/weblogs/viewpost.jsp?thread=291467，這回答了我的問題。