Re: setting fields of object using traits

[Jacob Carlborg via Digitalmars-d-learn]

On 2016-09-20 21:45, Ram_B wrote:

I'm trying to set fields of object from JSON with traits library. How i
can to it properly?

import std.stdio;
import std.json;
import std.traits;
import std.meta:  Alias;

class Obj{
void fromJSON(this T)(JSONValue j){
foreach(field; FieldNameTuple!T){
alias member = Alias!(__traits(getMember, T, field));
static if (__traits(hasMember, member, "fromJSON")){
member.fromJSON(j[field]);
} else {
member = j[field];


I'm pretty sure this won't work. You need to use "this.tupleof[index] = 
value" to set a value. You can iterate all fields using "T.tupleof" and 
then get the name of a field using "__traits(identifier, 
T.tupleof[index]);". Or you can use a string mixin.


--
/Jacob Carlborg

setting fields of object using traits

[Ram_B via Digitalmars-d-learn]

I'm trying to set fields of object from JSON with traits library. 
How i can to it properly?


import std.stdio;
import std.json;
import std.traits;
import std.meta:  Alias;

class Obj{
void fromJSON(this T)(JSONValue j){
foreach(field; FieldNameTuple!T){
alias member = Alias!(__traits(getMember, T, field));
static if (__traits(hasMember, member, "fromJSON")){
member.fromJSON(j[field]);
} else {
member = j[field];
}
}
}
}

class A : Obj{
int a,b;
C c;
this(){
c = new C();
}

}

class C : Obj{
int a;
this(){
a = 0;
};
}

int main(string[] argv)
{
string s = "{\"a\": 1, \"b\": 2, \"c\": {\"a\": 3} }";
JSONValue j = parseJSON(s);
A a = new A();
a.fromJSON(j);
writeln(a.b);
readln();
return 0;
}

main.d(14): Error: need 'this' for 'a' of type 'int'
main.d(14): Error: need 'this' for 'b' of type 'int'
main.d(12): Error: template main.Obj.fromJSON cannot deduce 
function from argument types !(c)(JSONValue), candidates are:

main.d(8):main.Obj.fromJSON(this T)(JSONValue j)
main.d(41): Error: template instance main.Obj.fromJSON!(A) error 
instantiating