Question: Written in the book:
--------------------
Class reference is a type, it is not a reference to the object, nor is it a reference to a class,
It is a reference for the type of class. The reference type of the class defines the type of reference variable.
Suppose the user defines a class:
Type
CMYCLASS = Class
...
end
The following is defined below, the reference type of the category is related to the following class:
Type
MyclassRef = Calss of CMYCLASS
This declares two types of variables:
ACLASSREF: MyClassRef;
AOBJECT: CMYCLASS;
The first variable references an object, the second reference class:
Aclassref = CMYCLASS;
AOBJECT = CMYCLASS.CREATE;
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I can't understand this paragraph, please explain it. Thank you
From: PIPI., Time: 2002-2-8 23:13:00, ID: 916427 Also hold an example, such as I can write a function
TYPE TCONTROLCLASS = Class of tcontrol;
Procedure INSERT_CONTROL (CLS: TCONTROLCLASS);
Begin
Obj; = CLS.CREATE (Application);
Put Obj into FORM
END;
When you call, if you are INSERT_CONTROL (TEDIT), put it in FORM is an edit box.
If INSERT_CONTROL (TButton) is then put into FORM is a button
Thank you is
VAR CTL: TControlClass;
CTR: = TEDIT;
INSERT_CONTROL (CTL)
------------------------------
Note that we use TButton and Tedit that they have common ancestors TControl
We define a base class and then pass the different subclasses, then a function only writes a different effect.
From: Holyowl, Time: 2002-2-8 23:26:00, ID: 916440 The use of the reference is to create an object that cannot be determined in the compiler, lifting a list:
Type
Tcontrolcls = Class of tcontrol;
Function CreateComponent (Controlcls: tcontrolcls): tcontrol;
Begin
Result: = Controlcls.create (Form1);
...
END;
When calling:
CreateComponent (TMEMO); // Creating a TMEMO object
CreateComponent (TEDIT); // Create TEDIT object
From: Renrf, Time: 2002-2-9 0:07:00, ID: 916478 Thank you,
How is the example in my book understand?
From: PIPI., Time: 2002-2-9 0:29:00, ID: 916503 The example of your book is simpler, did not talk about the actual use at all
Just a place where ACLASSREF appears, you look into CMYCLASS.
From: TestNet, Time: 2002-2-16 1:17:00, ID: 923102 in advance, I haven't seen it yet
Type
Tcontrolcls = Class of tcontrol;
Function CreateComponent (Controlcls: TcontrolCls): tcontrol; begin
Result: = Controlcls.create (Form1);
...
END;
Function CreateComponent (Controlcls: tcontrol): tcontrol;
Begin
Result: = Controlcls.create (Form1);
...
END;
Is the result of these two stuff? What difference will there be? ? I only pay attention to the result
From: PIPI., Time: 2002-2-16 1:26:00, ID: 923112 is of course different
From: Beta, Time: 2002-2-16 2:34:00, ID: 923171to TestNet:
Change your two function names to CreateComponent1 and CreateComponent2
You are like this:
CreateComponent1 (TEDIT);
CreateComponent2 (TEDIT);
See the difference in the results?
From: Beta, Time: 2002-2-16 2:35:00, ID: 923172 The former requires the introduction of a class, while the latter requires access to an object (instance of class)
From: Beta, Time: 2002-2-16 2:43:00, ID: 923174 The previous function will create an instance of the class you incorporated, and the latter function, there is no meaning.
From: JHDANDCL, Time: 2002-2-16 10:53:00, ID: 923281 is more clear,
Type
MyclassRef = Calss of CMYCLASS / / indicates that myclassRef is a pointer to CMYCLASS or its parent class.
From: Leasun, Time: 2002-2-16 11:37:00, ID: 923316 The reference is like a pointer to the class.
From: TestNet, Time: 2002-2-16 12:41:00, ID: 923408 This feature is good
From: xiangya, Time: 2002-2-21 1:33:00, ID: 931109 | Editor did not say clear! [: D] See the explanation here:
Accurately, this is the original secondary identification of the compiler.
"I defined a lot of classes, of course, they are a system, then, I will become a certain type,
When you need an instance of a class or class (usually the latter), you will tell me the name of that class.
Then, I will give you the class, or the instance of the class. "In fact, this is not clear, behind,
"You are a pig, pig, he is a horse, horse, I am a head, human,"
Ok, "We are all called animal categories (there are animal categories in actual life [?] No!
It's all abstract concepts) So, the example of animal category we call a certain animal.
Now, the slaughterhouse should buy an animal, good! Is it a pig? Is it a horse? [?] No, it will not be a person.
In this way, we send a pig or horse (remember, this is type), no matter how, the slaughterhouse will get an animal.
Finally, some human instances have to eat [: D]
Think about it, then the following,
Type
Tcontrolcls = Class of tcontrol;
Function CreateComponent (Controlcls: tcontrolcls): tcontrol;
/ / Here is asking "Are you sending a horse or a pig? [?]"
/ / The result, the following code sent a window class [:)]
Begin
Result: = Controlcls.create (Form1);
...
END;
Function CreateComponent (Controlcls: tcontrol): tcontrol;
// Ask, you want the pig [?]
// A: I want the window of the window [^]
Begin
Result: = Controlcls.create (Form1);
...
END;
Ok, if you don't understand it, it is a pig. [:)] The last expression: What type of type you need, well, you tell me the type you want, I will build a such object.
[: (!] [:(!] Declare, don't misunderstand, I don't swear, I want to say this, your impression is very deep and better understood.
