Define methods using templates

[Claude via Digitalmars-d-learn]

Hello, I'm trying to use templates to define several methods 
(property setters) within a class to avoid some code duplication.
Here is an attempt:

class Camera
{
private:
     Vector4 m_pos;
     float m_fov, m_ratio, m_near, m_far;
     bool m_matrixCalculated;

public:
     void SetProperty(Tin, alias Field)(ref Tin param) @property 
pure @safe
     {
         Field = param;
         m_matrixCalculated = false;
     }

     alias pos   = SetProperty!(float[], m_pos);
     alias pos   = SetProperty!(Vector4, m_pos);
     alias ratio = SetProperty!(float,   m_ratio);
     alias near  = SetProperty!(float,   m_near);
     alias far   = SetProperty!(float,   m_far);
}

I get this kind of compilation error:
Error: template instance SetProperty!(float[], m_pos) cannot use 
local 'm_pos' as parameter to non-global template 
SetProperty(Tin, alias Field)(ref Tin param)

I don't understand why that error occurs.

And I cannot find any elegant solutions (even with mixin's) to 
declare a template and then instantiate it in a single line to 
define the methods I want.

Does any of you have an idea?

Thanks