How to access private methods without helpers?

Question

In Delphi 10 Seattle I could use the following code to work around overly strict visibility restrictions.

How do I get access to private variables?

Answer 1

If there is extended RTTI info generated for the class private members - fields and/or methods you can use it to gain access to them.

Of course, accessing through RTTI is way slower than it was through class helpers.

Accessing methods:

var
  Base: TBase2;
  Method: TRttiMethod;

  Method := TRttiContext.Create.GetType(TBase2).GetMethod('UsefullButHidden');
  Method.Invoke(Base, []);

Accessing variables:

var
  Base: TBase;
  v: TValue;

  v := TRttiContext.Create.GetType(TBase).GetField('FMemberVar').GetValue(Base);

---

Default RTTI information generated for RTL/VCL/FMX classes is following

• Fields - private, protected, public, published
• Methods - public, published
• Properties - public, published

Unfortunately, that means accessing private methods via RTTI for core Delphi libraries is not available. @LU RD's answer covers hack that allows private method access for classes without extended RTTI.

Working with RTTI