Sequelize calculate value before saving

问题

I want to calculate the difference in hours before saving a model. I have tried beforeUpdate (and other hooks), but the field is never calculated. I have also tried the set: option, but that doesn't work either.

I have to fields 'started_at' and 'ended_at'. If ended_at is not null, then calc difference and save to field hours.

I have tried:

hours: {
      type: DataTypes.DECIMAL(10,2),
      allowNull: true,
      set: function(){
        var duration = 0;
        if(this.ended_at){
          var Start = moment(this.started_at);
          var End = moment(this.ended_at);
          duration = End.diff(Start, 'hours', true);   
        }
        this.setDataValue('hours', duration);
      }
    },

And I have tried:

beforeCreate: function(travel_log, options, fn){
        if(travel_log.ended_at){
          var Start = moment(travel_log.started_at);
          var End = moment(travel_log.ended_at);
          travel_log.hours = End.diff(Start, 'hours', true);
        }
        fn(null, travel_log)
      },

without any success. The documentation isn't really helpful either. Can anybody help? Thx

回答1:

As I mention in the comment I'm not sure of what you want, but you can create an instance, change the variables of the instance. For example, if you have a model Task:

var task = Task.build();
task.hours = CalcHoursExample();
task.save();

Hope this helps

回答2:

InstanceMethods are needed...

instanceMethods: {
      calcHours: function(started_at,ended_at){
        var duration = 0;
        if(ended_at){
          var Start = moment(started_at);
          var End = moment(ended_at);
          var duration = End.diff(Start, 'hours', true);

        }
        return duration;
      }
    },

So in the hooks:

beforeCreate: function(travel_log, options, fn){
        travel_log.hours = travel_log.calcHours(travel_log.started_at,travel_log.ended_at);
        fn(null, travel_log)
      },

来源：https://stackoverflow.com/questions/29183093/sequelize-calculate-value-before-saving