Question

我目前正在学习如何使用Knex，而且我无法按照正确的顺序运行我编写的函数。

当代码运行时，我期望发生的是删除表（如果存在），创建表，最后使用数据为表添加表。现在，播种功能在创建表之前运行，导致程序崩溃。

它应该在index.js中按以下顺序运行：main()＆gt; dropTables()＆gt; createTables()＆gt; seedTables()。

如何让这些功能以正确的顺序运行？

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

除了在箭头函数中调用return dbConnection...之外，您还应该返回创建的版本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) } }，并在调用之前等待。

#header {
   ...
   /* remove margin-top: 10px */
   padding-top: 10px; /* add */
   ...
}

#header { /* header extra code */
  position: fixed; /* fix it */
  top: 0; left: 0; /* to top/left */
  z-index: 1; /* above content */
  width: 100%; /* at full parent width (=> .container) */
  background: rgba(255,255,255,.9); /* hide 'scrolling under' content */
  /* with a bit transparency to see it scroll */
}

/* new line, move content down and a nice space below header */
.container>.row:nth-child(2) {
  padding-top: 6rem;
}

* {outline: 1px dashed } /* debug helper, remove when done */
/* so you can see what your element boxes look like*/

Knex JavaScript函数没有以等待的正确顺序执行

1 个答案: