我正在尝试实现一个配置文件类包装器,使用单个函数获取和使用单个函数将值设置为属性会更容易。
下面的代码是我试图实现的最低版本。
欢迎任何帮助。
unit Config;
interface
uses Rtti;
type
Group = class(TCustomAttribute)
strict private
FName: string;
public
constructor Create(const Name: string);
property Name: string read FName;
end;
IConfig = class
protected
function GetString: string;
procedure SetString(const Value: string);
end;
TConfig = class(IConfig)
public
[Group('Person')]
property Name: string read GetString write SetString;
[Group('Person')]
property City: string read GetString write SetString;
end;
implementation
{ Group }
constructor Group.Create(const Name: string);
begin
FName := Name;
end;
{ IConfig }
function IConfig.GetString: string;
begin
// Here I would need the following from the property that call this function:
// * Property name
// * Property attribute name
// This kind of code will not work, because it loop through all available properties
(*
var
ctx: TRttiContext;
objType: TRttiType;
Prop: TRttiProperty;
begin
ctx := TRttiContext.Create;
objType := ctx.GetType(Obj.ClassInfo);
for Prop in objType.GetProperties do begin
if Prop.GetClassType is TClassBase then
// do something special with base class properties
else
// standard functionality on all other properties
end;
end;
*)
end;
procedure IConfig.SetString(const Value: string);
begin
// Need the same as above
end;
end.
答案 0 :(得分:7)
属性getter和setter不知道哪个属性正在调用它们。共享getter / setter知道的唯一方法是使用index
说明符,例如:
unit Config;
interface
uses Rtti;
type
Group = class(TCustomAttribute)
strict private
FName: string;
public
constructor Create(const Name: string);
property Name: string read FName;
end;
IConfig = class
protected
function GetString(Index: Integer): string;
procedure SetString(Index: Integer; const Value: string);
end;
TConfig = class(IConfig)
public
[Group('Person')]
property Name: string index 0 read GetString write SetString;
[Group('Person')]
property City: string index 1 read GetString write SetString;
end;
implementation
{ Group }
constructor Group.Create(const Name: string);
begin
FName := Name;
end;
{ IConfig }
function IConfig.GetString(Index: Integer): string;
begin
case Index of
0: begin // Name
...
end;
1: begin // City
...
end;
...
end;
end;
procedure IConfig.SetString(Index: Integer; const Value: string);
begin
// same as above
end;
end.
如果getter / setter需要知道属性名称,您可以使用RTTI查找具有相应index
值的属性,如果找到,那么您还可以访问其属性,例如:< / p>
function GetPropNameAndGroup(Cls: TClass; PropIndex: Integer; var PropName, GroupName: String): Boolean;
var
Ctx: TRttiContext;
Prop: TRttiProperty;
Attr: TCustomAttribute;
begin
PropName := '';
GroupName := '';
Ctx := TRttiContext.Create;
for Prop in Ctx.GetType(Cls).GetProperties do
begin
if (Prop as TRttiInstanceProperty).Index = PropIndex then
begin
PropName := Prop.Name;
for Attr in Prop.GetAttributes do
begin
if Attr is Group then
begin
GroupName := Group(Attr).Name;
Break;
end;
end;
Break;
end;
end;
Result := (PropName <> '') and (GroupName <> '');
end;
function IConfig.GetString(Index: Integer): string;
var
PropName, GroupName: string;
begin
if GetPropNameAndGroup(ClassType, Index, PropName, GroupName) then
begin
//...
end;
end;
procedure IConfig.SetString(Index: Integer; const Value: string);
var
PropName, GroupName: string;
begin
if GetPropNameAndGroup(ClassType, Index, PropName, GroupName) then
begin
//...
end;
end;
答案 1 :(得分:0)
属性getter或setter无法确定访问了哪个属性导致调用getter或setter。
该陈述的必然结果是你要求做的事是不可能的。
至于如何解决你的潜在问题,我不会太在意太多细节。 property index access specifiers可能对您有用,这似乎是合理的。但是,如果不了解您所面临的实际问题,我就没有资格了解更多细节。