Let's talk OOP Again

Let’s talk OOP again

You will encounter same problem, no matter what kind of software products you design or develop:

how to design “User Object”?

I usually design “User Object” like this (The following is a simple example):

I think most of us design “User Object” like this.

En , looked as if there is no problems , Moreover ,it had became some people's habit

We do like design “Add method” like “Add(xxx,xxx,xxx,xxx,xxx,xxx)”

But, when I review some base OOP knowledge recently; I found there is something wrong.

So, I change my old design(The following is sample example too):

If you can see I mind? Why “Example1” change to “Example2”?

Two important changes at there:

1, I use “Property” replace “public variable”;

public virtual string UserName

...{

get ...{ return _userName; }

set

...{

if (_userName != value)

...{

if (value.Length > 16||value.Length<4)

...{

throw new Exception("you can input 4-16 characters to UserID only");

}

if(...)

...{

throw new Exception("... ...")

}

if(...)

...{

throw new Exception("... ...")

}

_userName = value;

}

2, I use “Add (User xxx)” replace “Add (XXX,XXX,XXX)”;

Do you know why?

First, Use Property can get more control, the following code will show it:

You can code like this:

User objUser=new User();

Users objUser=new Users();

User.userName=TxtUserName.Text.Trim();

User.Password=TxtPassword.Text;

objUser.Add(objUser);

Attention, if username is too long or short, “User Object” will throw a Exception, we can catch this exception.

If you use old design,your code maybe like this:

User objUser=new User();

String strUserName= TxtUserName.Text.Trim();

String strPassword=TxtPassword.Text;

If(strUserName >16|| strUserName <4)

...{

… …

}

objUser.Add(strUserName,strPassword);

Which one more easy ?

Second, Like those method:”add”, “update” etc, use Object as parameter better than variable, It is more easy. You can see it from above code.

Third, it is most important thing: “Add”, "Update” methods not belong to “User Object”, they should belong to “Users Object” or belong to “Dept Object”

I don’t know if you can understand the third. but you should try do it.

In this world, much thing we don’t know, but if when we try, we will get it

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