Advanced Programming Techniques in D/

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UDA Example

UDA Example

Let’s understand UDA with the help of an example.

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Example

Let’s design a function template that prints the values of all members of a struct object in XML format. The following function considers the Encrypted and Colored attributes of each member when producing the output:

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void printAsXML(T)(T object) {

//...



    foreach (member; __traits(allMembers, T)) {  // 1

        string value =

            __traits(getMember, object, member).to!string;  // 2



        static if (hasUDA!(__traits(getMember, T, member),  // 3

                           Encrypted)) {

            value = value.encrypted.to!string;

        }



        writefln(`  <%1$s color="%2$s">%3$s</%1$s>`,

                 member, colorAttributeOf!(T, member), value); // 4

    }

}

The numbered parts of the code are explained below:

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