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PORtti accessing fields and properties in complex data structures
 

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    <p>As already discussed in <a href="https://stackoverflow.com/questions/2771864/rtti-data-manipulation-and-consistency-in-delphi-2010">Rtti data manipulation and consistency in Delphi 2010</a> a consistency between the original data and rtti values can be reached by accessing members by using a pair of TRttiField and an instance pointer. This would be very easy in case of a simple class with only basic member types (like e.g. integers or strings). But what if we have structured field types?</p> <p>Here is an example:</p> <pre><code>TIntArray = array [0..1] of Integer; TPointArray = array [0..1] of Point; TExampleClass = class private FPoint : TPoint; FAnotherClass : TAnotherClass; FIntArray : TIntArray; FPointArray : TPointArray; public property Point : TPoint read FPoint write FPoint; //.... and so on end; </code></pre> <p>For an easy access of Members I want to buil a tree of member-nodes, which provides an interface for getting and setting values, getting attributes, serializing/deserializing values and so on.</p> <pre><code>TMemberNode = class private FMember : TRttiMember; FParent : TMemberNode; FInstance : Pointer; public property Value : TValue read GetValue write SetValue; //uses FInstance end; </code></pre> <p>So the most important thing is getting/setting the values, which is done - as stated before - by using the GetValue and SetValue functions of TRttiField.</p> <p>So what is the Instance for FPoint members? Let's say Parent is the Node for TExample class, where the instance is known and the member is a field, then Instance would be:</p> <pre><code>FInstance := Pointer (Integer (Parent.Instance) + TRttiField (FMember).Offset); </code></pre> <p>But what if I want to know the Instance for a record property? There is no offset in this case. So is there a better solution to get a pointer to the data?</p> <p>For the FAnotherClass member, the Instance would be:</p> <pre><code>FInstance := Parent.Value.AsObject; </code></pre> <p>So far the solution works, and data manipulation can be done by using rtti or the original types, without losing information.</p> <p>But things get harder, when working with arrays. Especially the second array of Points. How can I get the instance for the members of points in this case?</p>
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