typescript 遍历angular2打字稿中的数组
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Iterating through an array in angular2 typescript
提问by Geoff
Am new to typescript and angular2 and learnining this and i have this issue. I have a form that i would like to show the results of an array of items but these items keep changing everytime so i dont now the actual index of the returned results.
我是 typescript 和 angular2 的新手，正在学习这个，我有这个问题。我有一个表格，我想显示一组项目的结果，但这些项目每次都在不断变化，所以我现在不知道返回结果的实际索引。
This is the case
这是这种情况
I have this form.html
我有这个 form.html
<span style="color:red">{{usererror.username}} </span>
...other items here
<span style="color:red">{{usererror.password}} </span>
Now in the component
现在在组件中
export class LoginComponent implements OnInit{
public usererror={
username:"",
password:""
}
//this function is called after a post request
onLoginError(error:any){
let message= JSON.parse( error._body);
console.log(error._body); //first log
console.log(message) //second log
}
}
As from the above function the first log returns an array of the form
从上面的函数中，第一个日志返回一个数组
[{"field":"username","message":"Username cannot be blank."},
{"field":"password","message":"Password cannot be blank."}]
Now i would like to assign the username and password variables in the above usererror so that they can be displayed
现在我想在上面的 usererror 中分配用户名和密码变量，以便它们可以显示
So something like this
所以像这样
onLoginError(error:any){
let message= JSON.parse( error._body);
let message= JSON.parse( error._body);
for (var i=0; i<message.length; i++){
this.usererror.message[i].field = message[i].message; //this fails since the
//usererror doesnt have (message[i].field) property
}
}
sometimes the returned results dont have a username field and sometimes the password field. How do i go about this, am still new to angular2 and typescript
有时返回的结果没有用户名字段，有时没有密码字段。我该怎么做，我还是 angular2 和 typescript 的新手
回答by n00dl3
Use the square bracket notation (object["property"]) :
使用方括号符号 ( object["property"]) ：
let messages= JSON.parse( error._body);
for (let message of messages){
if(this.usererror[message.field])
this.usererror[message.field]=message.message;
}
回答by Jason Evans
If all you require is to check whether this.usererror.message[i].fieldexists, before attempting to copy the message, then you can include an ifstatement like this:
如果您只需要this.usererror.message[i].field在尝试复制消息之前检查是否存在，那么您可以包含如下if语句：
for (var i=0; i<message.length; i++){
if(this.usererror.message[i].field){
this.usererror.message[i].field = message[i].message;
}
}
If the field is undefined, as in it does not exist, then that ifstatement will return false.
如果该字段是undefined，因为它不存在，那么该if语句将返回false。
