Sails.js associations

问题:

I am beginning with sails.js and I am completely lost with my sql queries.

I have the following tables :

genres +-----------+--------------+------+-----+ | Field     | Type         | Null | Key | +-----------+--------------+------+-----+ | id        | int(6)       | NO   | PRI |  | name      | varchar(100) | NO   |     |  | slug      | varchar(255) | NO   |     | | type      | varchar(32)  | NO   |     |  | parent_id | int(11)      | YES  | MUL |  +-----------+--------------+------+-----+ genres_radios +----------+--------+------+-----+ | Field    | Type   | Null | Key | +----------+--------+------+-----+ | genre_id | int(6) | NO   | MUL | | radio_id | int(6) | NO   | MUL | +----------+--------+------+-----+ radios +-----------+--------------+------+-----+ | Field     | Type         | Null | Key | +-----------+--------------+------+-----+ | id        | int(5)       | NO   | PRI |  | name      | varchar(100) | NO   |     |  | slug      | varchar(100) | NO   |     | | url       | varchar(100) | NO   |     |  +-----------+--------------+------+-----+ 

I want to retrieve the radios and their associated genres. I managed to do it using the Model.query("Select * FROM ...") but I'd like to do it using the populate method. I had a look at the docs, but I am a bit confused with the "via", "through", ...

回答1:

This should do it :

// api/models/Genres.js module.exports = {     attributes : {         name : {             type: 'string'         },         slug : {             type: 'string'         },         type : {             type: 'string'         },         radios : {             collection: 'Radios',             through: 'genres_radios'         }      } }  // api/models/Radios.js module.exports = {     attributes : {         name : {             type: 'string'         },         slug : {             type: 'string'         },         url : {             type: 'string'         },         genres : {             collection: 'genre',             through: 'genres_radios'         }     } }  // api/models/Genres_radios.js module.exports = {     attributes = {         'Genre_id': {             columnName:'genre_id',             type:'integer',             foreignKey:'true',             references:'genres',             on:'id',             via:'genres'         },         'Radio_id': {             columnName:'radio_id',             type:'integer',             foreignKey:'true',             references:'radios',             on:'id',             via:'radios'         }     } } 

And then you can make the following request :

Radio.findOne({name:"RadioName"}).populate("genres").then(function(radio){     console.log(radio);  }) 

回答2:

Well if you've followed the Sails.js Model documentation and the many-many association docs your models should look something like:

// api/models/genre.js module.exports = {     attributes : {         name : {             type: 'string'         },         slug : {             type: 'string'         },         type : {             type: 'string'         },         radios : {             collection: 'radio',             via: 'genres'         }      } }  // api/models/radio.js module.exports = {     attributes : {         name : {             type: 'string'         },         slug : {             type: 'string'         },         url : {             type: 'string'         },         genres : {             collection: 'genre',             via: 'radios'         }      } } 

The many-many lookup table will be created for you internally by waterline. All you need to get the genres for your radio is populate the "genres" attribute.

Radio.findOne({name:"RadioName"}).populate("genres").then(function(radio){     console.log(radio); //radio.genres will have all the genres associated with this radio.  }) 

I really do recommend looking at the many-many association docs. They have exactly what you need.

文章来源: Sails.js associations