Question

尝试切换出Mongo并放入Postgres（换句话说，类似的代码与Mongo一起工作正常）。获取Cannot read property 'length' of undefined以下代码。我确信这很简单，但我是整个堆栈的新手，因此无法将它们捆绑在一起。关于knex的例子不多，所以即使文档非常好，我也很难找到要复制的例子。

我显然正在提取正确的数据，但我仍坚持如何让玉石显示它。

Stack：Node / Express / Knex / Postgres / Jade

users.js

router.get('/', function(req, res, next) {
  db.select().from('users').limit(1)
    .then(function(users) {
        console.dir(users)})
    .then(function(users) {
        res.render('users', {users: users})})
    .catch(function(error) {
        console.error(error)
  })
});

users.jade

extends layout

block content
  h1 Users
  ul
    for user in users
      p 
        input(type="text", name="name", value="#{user.name}")
        input(type="text", name="admin", value="#{user.admin}")
        input(type="text", name="smsNumber", value="#{user.smsNumber}")

控制台

[ { uid: 1,
    name: 'Don',
    admin: 'true',
    smsNumber: '4077023951',
    created_at: null,
    updated_at: null } ]

localhost：3000 / users

的浏览器

C:\Users\dvande03\Personal\dailychallenge\views\users.jade:6 4| h1 Users 5| ul > 6| for user in users 7| p 8| input(type="text", name="name", value="#{user.name}") 9| input(type="text", name="admin", value="#{user.admin}") Cannot read property 'length' of undefined

TypeError: C:\Users\dvande03\Personal\dailychallenge\views\users.jade:6
    4|   h1 Users
    5|   ul
  > 6|     for user in users
    7|       p 
    8|         input(type="text", name="name", value="#{user.name}")
    9|         input(type="text", name="admin", value="#{user.admin}")

Cannot read property 'length' of undefined
    at eval (eval at <anonymous> (C:\Users\dvande03\Personal\dailychallenge\node_modules\jade\lib\index.js:218:8), <anonymous>:51:31)
    at eval (eval at <anonymous> (C:\Users\dvande03\Personal\dailychallenge\node_modules\jade\lib\index.js:218:8), <anonymous>:106:4)
    at eval (eval at <anonymous> (C:\Users\dvande03\Personal\dailychallenge\node_modules\jade\lib\index.js:218:8), <anonymous>:119:22)
    at res (C:\Users\dvande03\Personal\dailychallenge\node_modules\jade\lib\index.js:219:38)
    at Object.exports.renderFile (C:\Users\dvande03\Personal\dailychallenge\node_modules\jade\lib\index.js:380:38)
    at Object.exports.renderFile (C:\Users\dvande03\Personal\dailychallenge\node_modules\jade\lib\index.js:370:21)
    at View.exports.__express [as engine] (C:\Users\dvande03\Personal\dailychallenge\node_modules\jade\lib\index.js:417:11)
    at View.render (C:\Users\dvande03\Personal\dailychallenge\node_modules\express\lib\view.js:126:8)
    at tryRender (C:\Users\dvande03\Personal\dailychallenge\node_modules\express\lib\application.js:639:10)
    at EventEmitter.render (C:\Users\dvande03\Personal\dailychallenge\node_modules\express\lib\application.js:591:3)
    at ServerResponse.render (C:\Users\dvande03\Personal\dailychallenge\node_modules\express\lib\response.js:961:7)
    at C:\Users\dvande03\Personal\dailychallenge\routes\users.js:11:13
    at tryCatcher (C:\Users\dvande03\Personal\dailychallenge\node_modules\bluebird\js\main\util.js:24:31)
    at Promise._settlePromiseFromHandler (C:\Users\dvande03\Personal\dailychallenge\node_modules\bluebird\js\main\promise.js:454:31)
    at Promise._settlePromiseAt (C:\Users\dvande03\Personal\dailychallenge\node_modules\bluebird\js\main\promise.js:530:18)
    at Promise._settlePromises (C:\Users\dvande03\Personal\dailychallenge\node_modules\bluebird\js\main\promise.js:646:14)

Answer 1

res.render应如下所示：let spawnAction = SKAction.repeatActionForever( SKAction.sequence([ SKAction.waitForDuration(2), SKAction.runBlock({ [unowned self] in self.spawnEnemy() }) ]) ) runAction(spawnAction)，其中res.render(view [, locals] [, callback])是一个对象，其属性定义视图的局部变量。在您的情况下，这意味着将您渲染的行更改为：

locals

传递一个带有局部变量的对象进行渲染。在jade文件中，当您想要引用值时，可以使用对象中的键。

Answer 2

解决了它，但我不完全理解为什么。我在渲染之前注释掉了console.dir并且它可以工作。这是因为console.dir .then中的用户没有传递给渲染.then吗？

我也接受了上面的答案，因为没有它，我就无法到达这里。谢谢@tomtom。

Knex / Jade：无法读取未定义的属性“长度”

2 个答案: