How to Define Template Function Within Template Class in *.Inl File

How to define template function within template class in *.inl file

Here's your definition:

template <typename T1, typename T2>
template <typename E>
void SomeClass<T1, T2>::extraTypedMethod(E & e)
{
}

Using template methods inside template classes

Why is it expecting Struct1

Because that is the type it was told to use.

Given the template:

template<typename Type>
class GenericClass
{
private:
    Type Identifier;

public:
    void setIdentifier(Type Param);
    Type getIdentifier();
};

The instantiation with type Struct1 (GenericClass<Struct1>) generates the following implementation:

// Just for illustration
class GenericClassStruct1
{
private:
    Struct1 Identifier;

public:
    void setIdentifier(Struct1 Param);
    Struct1 getIdentifier();
};

The above class has replaced all occurrences of Type with Struct1. Now, it should be easy to see why calling setIdentifier expects a Struct1 and not an int.

how do I format it so I can modify the properties in any struct

There is more than one way to do this. What is the "right" way will depend on the constraints of your problem but following example shows one way.

Example

Working Example

#include <iostream>

// Declared but not defined, specializations will provide definitions
template<typename T>
struct GenericTypeTraits;

template<typename T>
class Generic
{
public:
    using IdType = typename GenericTypeTraits<T>::IdType;

    void setIdentifier(IdType id)
    {
        mType.mIdentifier = id;
    }

    IdType getIdentifier() const
    {
        return mType.mIdentifier;
    }

private:
    T mType;
};

class Type1
{
public:
    int mIdentifier;
};

template<>
struct GenericTypeTraits<Type1>
{
    using IdType = int;
};

class Type2
{
public:
    std::string mIdentifier;
};

template<>
struct GenericTypeTraits<Type2>
{
    using IdType = std::string;
};

int main()
{
    Generic<Type1> t1[5];
    t1[0].setIdentifier(3);
    std::cout << t1[0].getIdentifier() << "\n";

    Generic<Type2> t2[5];
    t2[0].setIdentifier("3");
    std::cout << t2[0].getIdentifier() << "\n";

    return 0;
}

Output

3
3

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