Importing anuglar2/forms causing “Cannot read prop

问题:

I'm trying to create simple form as described in http://angularjs.blogspot.no/2015/03/forms-in-angular-2.html, but when I add

import {forms, required} from 'angular2/forms';

in crashes with

TypeError: Cannot read property 'annotations' of undefined

TypeError: Cannot read property 'annotations' of undefined
    at ReflectionCapabilities.System.register.execute.$__export.annotations (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/reflection/reflection_capabilities.es6!eval:81:40)
    at Reflector.System.register.execute.$__export.annotations (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/reflection/reflector.es6!eval:81:50)
    at DirectiveMetadataReader.System.register.execute.$__export.read (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/compiler/directive_metadata_reader.es6!eval:31:41)
    at eval (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/compiler/compiler.es6!eval:127:35)
    at Array.map (native)
    at Function.System.register.execute.$__export.map (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/facade/collection.es6!eval:172:26)
    at Compiler.System.register.execute.$__export.createSteps (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/compiler/compiler.es6!eval:126:43)
    at Compiler.System.register.execute.$__export._compileTemplate (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/compiler/compiler.es6!eval:164:53)
    at eval (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/compiler/compiler.es6!eval:154:29)
    at Zone.run (http://localhost:9090/node_modules/zone.js/zone.js:87:19)

-----async gap-----
Error
    at Function.System.register.execute.$__export.then (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/facade/async.es6!eval:35:28)
    at Compiler.System.register.execute.$__export._compile (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/compiler/compiler.es6!eval:153:42)
    at Compiler.System.register.execute.$__export.compile (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/compiler/compiler.es6!eval:134:34)
    at eval (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/application.es6!eval:73:23)
    at Function.System.register.execute.$__export.apply (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/facade/lang.es6!eval:317:23)

-----async gap-----
Error
    at _AsyncInjectorStrategy.System.register.execute._AsyncInjectorStrategy.instantiate (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/di/injector.es6!eval:297:17)
    at Injector.System.register.execute.$__export._getByKey (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/di/injector.es6!eval:138:33)
    at Injector.System.register.execute.$__export.asyncGet (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/di/injector.es6!eval:112:25)
    at eval (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/application.es6!eval:113:39)

-----async gap-----
Error
    at VmTurnZone.System.register.execute.$__export._createInnerZone (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/zone/vm_turn_zone.es6!eval:61:45)
    at new VmTurnZone (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/zone/vm_turn_zone.es6!eval:29:34)
    at _createVmZone (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/application.es6!eval:101:16)
    at bootstrap (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/application.es6!eval:110:16)
    at y.main (http://localhost:9090/app.js!eval:10:12)
    at http://localhost:9090/?:42:21

-----async gap-----
Error
    at VmTurnZone.System.register.execute.$__export._createInnerZone (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/zone/vm_turn_zone.es6!eval:61:25)
    at new VmTurnZone (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/zone/vm_turn_zone.es6!eval:29:34)
    at _createVmZone (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/application.es6!eval:101:16)
    at bootstrap (http://localhost:9090/node_modules/angular/dist/js/prod/es6/angular2/src/core/application.es6!eval:110:16)
    at y.main (http://localhost:9090/app.js!eval:10:12)
    at http://localhost:9090/?:42:21

Can't understand what that error message means, and I also can't find where is that forms directive defined.

UPDATE: the 'undefined' is actually a 'forms' directive which seems to be really missing in angular2/modules/angular2/src/forms. Then DirectiveMetadataReader passes the 'undefined' further to reflector which finally results in exception. Would be nice to have a check in Template.

回答1:

It looks like the example from Victor's blog didn't match the version you used (APIs were changing so fast those days). But now beta is released (and it means no more breaking changes) so I've created working example with as close as possible functionality:

Angular 2 Beta

import {Component} from 'angular2/core'
import {ControlGroup, FormBuilder, Validators} from 'angular2/common'
...

http://plnkr.co/edit/ae1WEgQJWPMdEgoweMGd?p=preview just to check how far it went (far enough!).

From Angular version: 2.0.0-rc.1

All imports that were using angular2 need to be changed to @angular

import {Component} from '@angular/core'
import {ControlGroup, FormBuilder, Validators} from '@angular/common';

For more List of imports see here :-

• List of all imports updated to angular2 RC.