Shulou(Shulou.com)06/02 Report--

Today, I will talk to you about how to use RTTI in Delphi. Many people may not know much about it. In order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

Summary

Runtime type information (RTTI) is a language feature that enables applications to get information about objects at run time.

RTTI is the key to the integration of Delphi components into IDE. It is not only a purely academic process in IDE.

Because objects inherit from TObject, objects contain a pointer to their RTTI and several built-in methods. The following table lists some of the methods of TObject that can be used to get information about an object instance.

Part one: about as and is

Object Pascal provides two operators, as and is, that allow you to compare and cast objects through RTTI.

The keyword as is a new form of type conversion. It can cast a grass-roots object type into its derived class, and an exception will be generated if the conversion is illegal. Suppose there is a process that wants it to be able to pass any type of object, it should be defined like this:

Procedure Foo (AnObject: Tobject)

If you want to operate on AnObject during this process, you need to convert it to a derived object. Suppose you think of AnObject as a TEdit derived type and want to change the text it contains, with the following code: (AnObject as Tedit) .text: = 'wudi_1982'

The comparison operator can be used to determine whether two objects are compatible types, and the is operator can be used to compare an unknown object with a known type or instance to determine the properties and behavior of the unknown object. For example, before casting (AnObject), determine whether (AnObject and TEdit are pointer compatible:

If (AnObject is Tedit) then

Tedit (AnObjject) .text: = 'wudi_1982'

Note that as is no longer used for casting in this example, because it uses RTTI a lot, and because it has been determined on the first line that Foo is TEdit, which can be optimized by pointer conversion on line 2.

Procedure TForm1.ClearEdit (Acontrl: TWinControl)

Var

I: integer

Begin

For I: = 0 to Acontrl.ControlCount-1 do

Begin

If Acontrl.Controls [i] is TEdit then

((Acontrl.Controls [I]) as TEdit) .Text: =''

If Acontrl.Controls [i] is TCustomControl then

ClearEdit ((Acontrl.Controls [I] as TCustomControl))

End

End

Part II: RTTI

RTTI has been mentioned many times above, but I don't seem to see RTTI. So how does RTTI express itself? You will find that RTTI is useful to you in at least two places. The first place is DELPHI's IDE, which was mentioned earlier. Through RTTI,IDE, you will know everything about the objects and components you are using. Actually, it's not just RTTI, but for this discussion, let's just talk about RTTI. In fact, the above as,is operations all indirectly use RTTI.

Let's use an example to demonstrate it. While viewing this example, it is recommended that you take a look at the contents of typinfo.pas (DELPHI installation directory / source/rtl/common/TypInfo.pas)

The following example is mainly divided into two parts, the top half of the interface, mainly demonstrates the use of rtti to display the type of information selected by the user. (there are 3 TListBox)

The following section mainly completes the assignment of properties to the control through configuration information through RTTI, which demonstrates the assignment of text types and event types.

The form file is as follows: the code is as follows:

Object Form1: TForm1

Left = 150

Top = 161,

Width = 639

Height = 372,

Caption = 'Form1'

Color = clBtnFace

Font.Charset = DEFAULT_CHARSET

Font.Color = clWindowText

Font.Height =-11

Font.Name = 'Tahoma'

Font.Style = []

OldCreateOrder = False

OnCreate = FormCreate

PixelsPerInch = 96

TextHeight = 13

Object Panel1: TPanel

Left = 0

Top = 0

Width = 631

Height = 185,

Align = alTop

TabOrder = 0

Object GroupBox1: TGroupBox

Left = 1

Top = 1

Width = 185,

Height = 183,

Align = alLeft

Caption = 'Select the type of information you want to view here'

TabOrder = 0

Object ListBox1: TListBox

Left = 2

Top = 15

Width = 181,

Height = 166,

Align = alClient

ItemHeight = 13

TabOrder = 0

OnClick = ListBox1Click

End

End

Object GroupBox2: TGroupBox

Left = 368

Top = 1

Width = 262,

Height = 183,

Align = alRight

Caption = 'attribute information'

TabOrder = 1

Object ListBox3: TListBox

Left = 2

Top = 15

Width = 258

Height = 166,

Align = alClient

ItemHeight = 13

TabOrder = 0

End

End

Object GroupBox3: TGroupBox

Left = 186

Top = 1

Width = 182

Height = 183,

Align = alClient

Caption = 'basic information'

TabOrder = 2

Object ListBox2: TListBox

Left = 2

Top = 15

Width = 178,

Height = 166,

Align = alClient

ItemHeight = 13

TabOrder = 0

End

End

End

Object TPanel

Left = 0

Top = 185,

Width = 631

Height = 157,

Align = alClient

TabOrder = 1

Object Panel2: TPanel

Left = 1

Top = 1

Width = 230

Height = 155

Align = alLeft

TabOrder = 0

Object Label2: TLabel

Left = 10

Top = 8

Width = 84

Height = 13

Caption = 'name of the control to be modified'

End

Object Label3: TLabel

Left = 8

Top = 32

Width = 72

Height = 13

Caption = 'modified attribute name'

End

Object Label4: TLabel

Left = 8

Top = 64

Width = 72

Height = 13

Caption = 'modify property to'

End

Object edComName: TEdit

Left = 104

Top = 5

Width = 78

Height = 21

TabOrder = 0

Text = 'label1'

End

Object edPproName: TEdit

Left = 104

Top = 32

Width = 81

Height = 21

TabOrder = 1

Text = 'caption'

End

Object edValue: TEdit

Left = 104

Top = 56

Width = 81

Height = 21

TabOrder = 2

Text = '12345'

End

Object btnInit: TButton

Left = 8

Top = 104

Width = 75

Height = 25

Caption = 'initialization'

TabOrder = 3

OnClick = btnInitClick

End

Object btnModify: TButton

Left = 104

Top = 104

Width = 75

Height = 25

Caption = 'modify'

TabOrder = 4

OnClick = btnModifyClick

End

End

Object Panel3: TPanel

Left = 231

Top = 1

Width = 399

Height = 155

Align = alClient

TabOrder = 1

Object GroupBox4: TGroupBox

Left = 1

Top = 1

Width = 397

Height = 153

Align = alClient

Caption = 'modified control'

TabOrder = 0

Object Label1: TLabel

Left = 16

Top = 32

Width = 28

Height = 13

Caption = 'label1'

End

Object BitBtn1: TBitBtn

Left = 8

Top = 64

Width = 75

Height = 25

Caption = 'BitBtn1'

TabOrder = 0

End

End

End

End

End

Unit main

Interface

Uses

Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls

Forms,Dialogs,typinfo, StdCtrls, ExtCtrls, Buttons

Type

InsertCom = record

Name: string; / / the name of the component to modify the property

PproName: string;// wants to modify the property name of the control

MethodName: string;// wants to modify the event name that or adds to the control

Text: string; / / attribute value. Here, the value of type string is modified.

End

TForm1 = class (TForm)

Panel1: TPanel

GroupBox1: TGroupBox

ListBox1: TListBox

GroupBox2: TGroupBox

GroupBox3: TGroupBox

ListBox2: TListBox

ListBox3: TListBox

Panel2: TPanel

EdComName: TEdit

Label2: TLabel

Label3: TLabel

EdPproName: TEdit

Label4: TLabel

EdValue: TEdit

Panel3: TPanel

BtnInit: TButton

BtnModify: TButton

GroupBox4: TGroupBox

Label1: TLabel

BitBtn1: TBitBtn

Procedure FormCreate (Sender: TObject)

Procedure ListBox1Click (Sender: TObject)

Procedure btnInitClick (Sender: TObject)

Procedure btnModifyClick (Sender: TObject)

Private

TestCom: InsertCom

Procedure MyClick (Sender: TObject); / / add an onclick event to the control

Public

{Public declarations}

End

Var

Form1: TForm1

Implementation

{$R * .dfm}

Function CreateClass (const AClassName: string): TObject;// is generated by name

Var

Tm: TObject

T: TFormClass

Begin

T: = TFormClass (FindClass (AClassName))

Tm: = t.Create (nil)

Result: = tm

End

Procedure GetBaseClassInfo (AClass: TObject;AStrings: TStrings); / / get basic information about the type

Var

ClassTypeInfo: PTypeInfo

ClassDataInfo: PTypeData

Begin

ClassTypeInfo: = AClass.ClassInfo

ClassDataInfo: = GetTypeData (classTypeInfo)

With AStrings do

Begin

Add (Format ('name is:% slots, [classTypeInfo.Name]))

Add (format ('type kind is:% slots, [GetEnumName (TypeInfo (TTypeKind), integer (classTypeInfo.Kind)])

Add (Format ('in:% slots, [ClassDataInfo.UnitName]))

End

End

Procedure GetBaseClassPro (AClass: TObject;Astrings: TStrings); / / get attribute information

Var

NumPro: number of integer; / / used to record event attributes

Pplst: PPropList; / / store attribute list

Classtypeinfo: PTypeInfo

ClassDataInfo: PTypeData

I: integer

Begin

Classtypeinfo: = AClass.ClassInfo

ClassDataInfo: = GetTypeData (Classtypeinfo)

If classDataInfo.PropCount 0 then

Begin

/ / allocate space

GetMem (Pplst,sizeof (PpropInfo) * classDataInfo.PropCount)

Try

/ / get attribute information to pplst

GetPropInfos (AClass.ClassInfo,Pplst)

For I: = 0 to classDataInfo.PropCount-1 do

Begin

If Pplst [I] ^ .PropType ^ .Kind tkMethod then

/ / event attributes are filtered out here

Astrings.Add (Format ('% slug% slots, [Pplst [I] ^ .Name, Pplst [I] ^ .PropType.Name]))

End

/ / get event attributes

NumPro: = GetPropList (AClass.ClassInfo, [tkMethod], Pplst)

If NumPro 0 then

Begin

/ / add some flags to the list

Astrings.Add ('')

Astrings.Add ('- EVENT-')

Astrings.Add ('')

For I: = 0 to NumPro-1 do / / get a list of event attributes

Astrings.Add (Format ('% slug% slots, [Pplst [I] ^ .Name, Pplst [I] ^ .PropType.Name]))

End

Finally

FreeMem (Pplst,sizeof (PpropInfo) * classDataInfo.PropCount)

End

End

End

Procedure TForm1.btnInitClick (Sender: TObject)

Begin

/ / modify the caption attribute of label1 to 12345

TestCom.Name: = edComName.Text

TestCom.PproName: = edPproName.Text

TestCom.text: = edValue.Text

TestCom.MethodName: = 'OnClick'

BtnModify.Enabled: = true

End

Procedure TForm1.btnModifyClick (Sender: TObject)

Var

Pp: PPropInfo

Obj: TComponent

A: TMethod

Tm: TNotifyEvent

Begin

Obj: = FindComponent (TestCom.Name); / / find this control by name

If not Assigned (obj) then exit; / / exit if not

/ / get the property information of the specified control through getPropInfo. Note that only those properties that have been disclosed can be obtained here.

Pp: = GetPropInfo (obj.ClassInfo,TestCom.PproName)

If Assigned (pp) then

Begin

/ / judge whether the type is string type according to kind

Case pp^ .PropType ^ .Kind of

/ / setStrProp is used to assign values to attributes of type string. For the assignment of types, please refer to TypInfo.pas

TkString,tkLString,tkWString: SetStrProp (obj,TestCom.PproName,TestCom.text)

End

/ / add an onClick event to the control to be modified

Pp: = GetPropInfo (obj.ClassInfo,TestCom.MethodName)

If Assigned (pp) then

Begin

If p ^ .PropType ^ .Kind = tkMethod then

Begin

Tm: = MyClick

/ / the code of Tmethod is the function address, which can also be obtained through the MethodAddress method.

A.Code: = @ tm

A.Data: = Self

/ / A pair of time assignments

SetMethodProp (obj,TestCom.MethodName,a)

End

End

End

End

Procedure TForm1.FormCreate (Sender: TObject)

Begin

BtnModify.Enabled: = false

/ / add some type class names to listbox1

With ListBox1.Items do

Begin

Add ('TApplication')

Add ('TEdit')

Add ('TButton')

Add ('Tmemo')

Add ('TForm')

End

End

Procedure TForm1.ListBox1Click (Sender: TObject)

Var

T: TObject

Begin

/ / when a type is selected in the type list and clicked with the mouse, its attribute information and basic information are obtained respectively.

ListBox2.Clear

ListBox3.Clear

T: = CreateClass (ListBox1.Items [ListBox1.ItemIndex])

Try

GetBaseClassInfo (tMagneListBox2.Items)

GetBaseClassPro (tMagneListBox3.Items)

Finally

T.Free

End

End

Procedure TForm1.MyClick (Sender: TObject)

Begin

/ / A method to add to a specified control

ShowMessage ('wudi_1982')

End

Initialization

/ / register at initialization

RegisterClasses ([TApplication,TButton,TEdit,TMemo,TForm])

After reading the above, do you have any further understanding of how to use RTTI in Delphi? If you want to know more knowledge or related content, please follow the industry information channel, thank you for your support.

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