如何将数据绑定到具有嵌套属性的命令对象？ （非域对象） [英] How to bind data to a command object that has a nested property? (non domain object)

问题描述

我试图将一些数据绑定到作为命令对象一部分的对象。该对象在尝试使用时保持为空。可能我没有在gsp中给出正确的数据，但我不知道我做错了什么！

我希望当我提交一个带有字段名称的表单'book.title'这将被映射到命令对象中，但是这会失败..标题保留[null]

每当我将命令对象和窗体更改为使用String title作为它的属性。

  //提交数据的表单
< g：form> ; 
 < br>< br> 
< g：actionSubmit action =createvalue =Create！/> 
< / g：表格> 
 
 
 //控制器代码
 def create = {BooksBindingCommand cmd  - > 
 println cmd？.book？.title //书属性总是保留为空
重定向（action：index）
} 
 
 //命令对象
 class BooksBindingCommand {
 Book book 
} 
 
 // book class，简单的普通groovy类
 class Book {
 String title 
} 
  

有关book.title绑定失败原因的任何建议？

解决方案

尝试在绑定之前对其进行初始化，例如：

  //命令对象
 class BooksBindingCommand {
 Book book = new Book（）
} 
  

I am trying to bind some data to an object that is part of a command object. The object stays null when trying to use it. Probably i am not giving the correct data in the gsp but i have no clue what am i doing wrong!

I would expect that when i submit a form with a field name 'book.title' this would get mapped into the command object.. but this fails.. The title stays [null]

Whenever i change the command object and form to use String title as property it works..

// the form that submits the data
<g:form>
   <g:textField name="book.title" value="Lord Of the Rings"/><br>
   <br><br>
   <g:actionSubmit action="create" value="Create!"/>
</g:form>


// the controller code
def create = { BooksBindingCommand cmd ->
   println cmd?.book?.title // the book property always stays null
   redirect(action: "index")
}

// the command object
class BooksBindingCommand {
   Book book
}

// the book class, simple plain groovy class
class Book {
   String title
}

Any suggestion on why the binding of 'book.title' fails?

解决方案

Try to initialize it before binding, like:

// the command object
class BooksBindingCommand {
   Book book = new Book()
}

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