Knex JavaScript函数未按正确的顺序执行

Question

I'm currently learning how to use Knex and I'm having trouble having the functions I've written run in the correct order.

When the code is run, what I'm expecting to happen is the tables are dropped (if they exist), the tables are created, and finally the tables are seeded with data. Right now the seeding function is running before the table creation which causes the program to crash.

It should run in the following order in index.js: main() > dropTables() > createTables() > seedTables() .

How do I get these functions to run in the correct order?

index.js

require("babel-core/register")
require("babel-polyfill")

import { makeUserTable, dropUserTable } from './models/users'
import { makeGameTable, dropGameTable } from './models/games'
import { seedUser } from './seeds/users'
import { seedGame } from './seeds/games'

const dbConnection = require('knex')({
  client: 'mysql',
  debug: false,
  connection: {
    host: 'localhost',
    user: 'samurai',
    password: 'bushido',
    database: 'knex_sandbox'
  }
})

function dropTables() {
  dropUserTable(dbConnection)
  dropGameTable(dbConnection)
}

function makeTables() {
  makeUserTable(dbConnection)
  makeGameTable(dbConnection)
}

function seedTables() {
  // seedUser(dbConnection)
  // seedGame(dbConnection)
  console.log('seed tables ran')
}

const main = () => {
  try {
    dropTables()
    makeTables()
    seedTables()

    // kill program
    dbConnection.destroy()
    console.log('===> Script done. Exiting.')
  } catch (err) {
    console.log('===> Something went wrong:\n', err)
  }
}

export default main(dbConnection)

models/users.js

export const makeUserTable = (dbConnection) => {
  dbConnection.schema
    .createTableIfNotExists('users', function (table) {
      table.increments('user_id').primary()
      table.string('username', 100)
      table.text('bio', 100)
    })
    .then(() => {
      console.log('===> User table created.')
    })
    .catch(err => {
      console.log('===> Something went wrong creating the user table:\n', err)
    })
}

export const dropUserTable = (dbConnection) => {
  dbConnection.schema
    .dropTableIfExists('users')
    .then(() => {
      console.log('===> User table dropped (if it exists).')
    })
    .catch(err => {
      console.log('===> Something went wrong dropping the user table:\n', err)
    })
}

models/games.js

export const makeGameTable = (dbConnection) => {
  dbConnection.schema
    .createTableIfNotExists('games', function (table) {
      table.increments('game_id')
        .primary()
      table.string('title', 100)
      table.text('description', 100)
      // table.integer('user_id')
      //   .unsigned()
      //   .references('users.user_id')
      //   .onDelete('cascade')
    })
    .then(() => {
      console.log('===> Game table created.')
    })
    .catch(err => {
      console.log('===> Something went wrong creating the game table:\n', err)
    })
}

export const dropGameTable = (dbConnection) => {
  dbConnection.schema
    .dropTableIfExists('games')
    .then(() => {
      console.log('===> Game table dropped (if it exists).')
    })
    .catch(err => {
      console.log('===> Something went wrong dropping the game table:\n', err)
    })
}

seeds/users.js

export const seedUser = (dbConnection) => {
  dbConnection
    .insert({
      username: 'dog',
      bio: 'Hello, this is dog'
    })
    .into('users')
    .then(() => {
      console.log('===> User seeded')
    })
    .catch(err => {
      console.log('===> Something went wrong seeding the user table:\n', err)
    })
}

seeds/games.js

export const seedGame = (dbConnection) => {
  dbConnection
    .insert({
      title: 'Bone',
      description: 'Om nom nom',
      // user_id: 1
    })
    .into('games')
    .then(() => {
      console.log('===> Game seeded')
    })
    .catch(err => {
      console.log('===> Something went wrong seeding the game table:\n', err)
    })
}

Answer 1

Instead of just calling dbConnection... in your arrow functions you should also return the created promise lie this return dbConnection... and put awaits back before calling them.

require("babel-core/register")
require("babel-polyfill")

import { makeUserTable, dropUserTable } from './models/users'
import { makeGameTable, dropGameTable } from './models/games'
import { seedUser } from './seeds/users'
import { seedGame } from './seeds/games'

const dbConnection = require('knex')({
  client: 'mysql',
  debug: false,
  connection: {
    host: 'localhost',
    user: 'samurai',
    password: 'bushido',
    database: 'knex_sandbox'
  }
})

async function dropTables() {
  await dropUserTable(dbConnection)
  await dropGameTable(dbConnection)
}

async function makeTables() {
  await makeUserTable(dbConnection)
  await makeGameTable(dbConnection)
}

async function seedTables() {
  // seedUser(dbConnection)
  // seedGame(dbConnection)
  console.log('seed tables ran')
}

const main = async () => {
  try {
    await dropTables()
    await makeTables()
    await seedTables()

    // kill program
    await dbConnection.destroy()
    console.log('===> Script done. Exiting.')
  } catch (err) {
    console.log('===> Something went wrong:\n', err)
  }
}