我加了引号表和列名,以使它们区分大小写:
CREATE TABLE "Currency" (
id INT, code VARCHAR(3), name TEXT
);
CREATE TABLE "ExchangeRate" (
"baseCurrencyId" INT, "counterCurrencyId" INT, rate FLOAT
);
INSERT INTO "Currency" (id, code, name) VALUES
(1, 'USD', 'US Dollars'),
(2, 'AUD', 'Australian Dollars');
INSERT INTO "ExchangeRate" ("baseCurrencyId", "counterCurrencyId", rate) VALUES
(1, 2, 1.342),
(2, 1, 0.745);
您可以模拟为多对多的关系,其中存储在额外的参数加入表:
const knex = require('knex')({
client: 'pg',
connection: 'postgres:///objection_test'
});
const { Model } = require('objection');
const Promise = require('bluebird');
class Currency extends Model {
static get tableName() { return 'Currency'; }
static get relationMappings() {
return {
currencyWithRate: {
relation: Model.ManyToManyRelation,
modelClass: Currency,
join: {
from: 'Currency.id',
through: {
from: 'ExchangeRate.baseCurrencyId',
to: 'ExchangeRate.counterCurrencyId',
extra: ['rate']
},
to: 'Currency.id'
}
}
};
}
}
const boundModel = Currency.bindKnex(knex);
boundModel.query().then(currencies => {
// get related currencies for each
return Promise.all(currencies.map(cur => {
return Promise.join(cur, cur.$relatedQuery('currencyWithRate'),
(cur, exchangeRateCurrency) => {
return {
currency: cur,
exchangeRateCurrency: exchangeRateCurrency
};
});
}));
}).then(result => {
console.dir(result, { depth: null});
}).finally(() => {
return knex.destroy();
});
让我们假设上面的代码是test.js:
Mikaels-MacBook-Pro-2: mikaelle$ node test.js
[ { currency:
AnonymousModelSubclass {
id: 1,
code: 'USD',
name: 'US Dollars',
currencyWithRate: [ AnonymousModelSubclass { id: 2, code: 'AUD', name: 'Australian Dollars', rate: 1.342 } ] },
exchangeRateCurrency: [ AnonymousModelSubclass { id: 2, code: 'AUD', name: 'Australian Dollars', rate: 1.342 } ] },
{ currency:
AnonymousModelSubclass {
id: 2,
code: 'AUD',
name: 'Australian Dollars',
currencyWithRate: [ AnonymousModelSubclass { id: 1, code: 'USD', name: 'US Dollars', rate: 0.745 } ] },
exchangeRateCurrency: [ AnonymousModelSubclass { id: 1, code: 'USD', name: 'US Dollars', rate: 0.745 } ] } ]
Mikaels-MacBook-Pro-2: mikaelle$
看起来像$relatedQuery()
也会向请求关系的Model
查询对象。
谢谢,相当详细的例子。我将不得不尝试一下,看看它是否可以解决我的问题:) – conny