问题描述
我想知道以下哪些被认为是在与父子关系处理是一个最佳实践。
I was wondering which of the following is considered to be a best practice when dealing with parent child relationships.
1)以下的例子似乎是一种常见的做法,但创建子的实例时,这将是处于无效状态,只要它不添加到父。莫非不是这导致有关验证等问题。
1) The following example seems to be a common practice, but when creating an instance of a child, it will be in an invalid state as long as it is not added to the parent. Couldn't this lead to problems regarding validation etc.
public class Parent
{
private ICollection<Child> children;
public ReadOnlyCollection Children { get; }
public void AddChild(Child child)
{
child.Parent = this;
children.Add(child);
}
}
public class Child
{
internal Parent Parent
{
get;
set;
}
public Child()
{
}
}
2)下一个示例会照顾,孩子必须始终与其父。
2) The next sample would take care that a child must always be related to its parent.
public class Parent
{
private ICollection<Child> children;
public ReadOnlyCollection Children { get; }
public Child CreateChild()
{
var child = new Child();
child.Parent = this;
children.Add(child);
return child;
}
}
public class Child
{
internal Parent Parent
{
get;
set;
}
internal Child()
{
}
}
3)在那个孩子取相对于它的母公司照顾最后一个例子。
3) In the last example that child takes care of the relation to its parent itself.
public class Parent
{
private ICollection<Child> children;
public ReadOnlyCollection Children { get; }
public void AddChild(Child child)
{
child.Parent = this;
children.Add(child);
}
}
public class Child
{
public Parent Parent
{
get;
set;
}
public Child(Parent parent)
{
this.Parent = parent;
}
}
哪个模式被认为是最好的?我相信这种模式2可能是最好的,因为那么一个孩子可以没有关系,其父永远存在。这将使它更容易例如落实可能做的事情一样的规范模式:
Which pattern is considered the best? I believe that pattern 2 might be the best since then a child can never exist without a relation to its parent. This would make it easier e.g. when implementing a specification pattern that might do things like:
public class ChildSpecification
{
bool IsSatisfiedBy(Child child)
{
return child.Parent.Children.Where(someCondition).Count > 0;
}
}
以上规格只能工作,如果一个孩子有父母。
The above specification can only work if a child has a parent.
你怎么看?你知道更好的方法?在此先感谢
What do you think? Do you know better ways? Thanks in advance
推荐答案
我绝对喜欢建议2号,但我认为它忽略一些重要的事情是在3个发现,即如果一个孩子
对象不能没有父
应采取父
在其构造对象存在。此外,父
的孩子
类的属性应为只读。所以,你最终会是这样的:
I definitely like suggestion number 2, but I think that it misses something important that is found in 3, namely that if a Child
object cannot exist without a Parent
it should take a Parent
object in its constructor. Furthermore the Parent
property on the Child
class should be read only.So you would end up with something like:
public class Parent
{
private ICollection<Child> children;
public ReadOnlyCollection Children { get; }
public Child CreateChild()
{
var child = new Child(this);
children.Add(child);
return child;
}
}
public class Child
{
internal Parent Parent
{
get;
private set;
}
internal Child(Parent parent)
{
this.Parent = parent;
}
}
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