ORM with default Values using RTTI and Property

[StraightFree]

Hello my friends,

I'm creating my own ORM.
I use the class TCrateDB to verify if database exists. If database not exists, I create it.

After this, I use RTTI to read Custom Attributes in my business classes to populate SQL statements and create the table.

Now, I want use some way to populate the database with values default, like this:

Table UNITS (auxiliary of Table PRODUCTS)

ID  |  DESCRIPTION  |  ABBREVIATION
-----------------------------------------------------
1    |  UNITY                | UN
-----------------------------------------------------
2    |  KILOGRAMA      | KG
-----------------------------------------------------
3    |  MILLILITER        |  ML

I think create a property with typekind TStringList with the values default.

Is there any way to retrieve the value of a property using RTTI?
I tried that way:

Code: Pascal  [Select][+][-]

1. var
2.  RCtx: TRttiContext;
3.  RType: TRttiType;
4.  Prop: TRttiProperty;
5. begin
6.   RCtx := TRttiContext.Create;
7.   try
8.     RType := RCtx.GetType(aClass);
9.     Prop := RType.GetProperty('Teste1');
10.  
11.     ShowMessage(Prop.Name);
12.     ShowMessage(Prop.GetValue("I do not know what to put here").ToString);
13.  
14.   finally
15.     RCtx.Free;
16.   end;
17. end;
18.  

Any help will be most welcome.

Thank you.

[dsiders]

Hello my friends,

I'm creating my own ORM.
I use the class TCrateDB to verify if database exists. If database not exists, I create it.

After this, I use RTTI to read Custom Attributes in my business classes to populate SQL statements and create the table.

Now, I want use some way to populate the database with values default, like this:

Table UNITS (auxiliary of Table PRODUCTS)

ID  |  DESCRIPTION  |  ABBREVIATION
-----------------------------------------------------
1    |  UNITY                | UN
-----------------------------------------------------
2    |  KILOGRAMA      | KG
-----------------------------------------------------
3    |  MILLILITER        |  ML

I think create a property with typekind TStringList with the values default.

Is there any way to retrieve the value of a property using RTTI?
I tried that way:

Code: Pascal  [Select][+][-]

1. var
2.  RCtx: TRttiContext;
3.  RType: TRttiType;
4.  Prop: TRttiProperty;
5. begin
6.   RCtx := TRttiContext.Create;
7.   try
8.     RType := RCtx.GetType(aClass);
9.     Prop := RType.GetProperty('Teste1');
10.  
11.     ShowMessage(Prop.Name);
12.     ShowMessage(Prop.GetValue("I do not know what to put here").ToString);
13.  
14.   finally
15.     RCtx.Free;
16.   end;
17. end;
18.  

Any help will be most welcome.

Thank you.

First, I would suggest another forum. FPC > General might have been the better choice since RTTI is an FPC feature and not a Lazarus-specific thing.

The test harness for RTTI (located in fpc/.../packages/rtl-objpas/tests/tests.rtti.pas) demonstrates the correct usage.

Getting the RTTI type should be:

Code: Pascal  [Select][+][-]

1. RType := RCtx.GetType(aClass.ClassInfo);

And, getting the property value should be:

Code: Pascal  [Select][+][-]

1. var AValue: TValue;
2. ...
3. AValue := Prop.GetValue(AClass);
4. ShowMessage(AValue.AsString)

Hope that helps...

[PascalDragon]

Is there any way to retrieve the value of a property using RTTI?

In addition to what dsiders wrote: please note that currently properties must be declared as published to be picked up.