node.js - sequelize CreateAssociation return parent instance instead of child created instance -

i have issue createassociation method.

here's code :

user create curves

//user create curves function savecurves(user, functions){    var curves = json.parse(functions);     (var = 0; < curves.length; i++) {        (function(i,user,curves){           user.createcurve({             i_min: curves[i].i_min,             i_max: curves[i].i_max,         }).then(function(curve){             savefunction(curve,curves[i].fn,curves[i].variables);         });     })(i,user,curves);     } }    //save function after creating curves depends on  function savefunction(curve,fct,variables){ return curve.createfunction({     fn: fct }).then(function(math_function){     savevariables(math_function,variables);     return; }) }   //save variables associated function function savevariables(fn, variables){ for(var j= 0; j < variables.length; j++){      (function(j,fn,variables){         fn.createvariable({             name: variables[j].name,             function_id: fn.id         })         .then(function(row_variable){             console.log(row_variable.tojson())             return row_variable.createfunction({                 fn: variables[j].fn             })     })(j,fn,variables);  } 

i have issue when i'm calling "fn.createvariable" method. don't understand why promise in .then after give me fn instance instead of variable instance.

and have error : unhandled rejection typeerror: row_variable.createfunction not function

when i'm looked database, saw instance has been correctly inserted row_variable in console.log give me fn , not inserted row.

so cannot understand have return. did above, why doesn't work here ?

(not relation definition issue because row exist in database)

any idea please ?