我正在尝试理解以下语法:
this.setState(currState => ({
...currState,
user: {
...currState.user,
[name]: value,
},
}));
我知道setState将通过影响组件的当前状态来更新此组件的状态,在这种情况下,将currentState和user对象合并为一个新状态。这是否意味着当我添加一个新用户A
然后添加第二个用户B
时,状态对象将同时具有A
和B
对象作为新状态,即两个user
对象?
class AddUser extends Component {
state = {
user: {
firstName: '',
lastName: '',
username: '',
},
userExists: false,
};
contactExists = currUsername => {};
handleSubmit = event => {};
handleInputChange = event => {
const { name, value } = event.target;
this.setState(currState => ({
...currState,
user: {
...currState.user,
[name]: value,
},
}));
};
isDisabled = () => {};
render() {
const { firstName, lastName, username } = this.state.user;
return (
<div>
<h1>New User</h1>
<form onSubmit={this.handleSubmit}>
<div>
<input
type="text"
name="firstName"
placeholder="Enter First Name"
value={firstName}
onChange={this.handleInputChange}
/>
<input
type="text"
name="lastName"
placeholder="Enter Last Name"
value={lastName}
onChange={this.handleInputChange}
/>
<input
type="text"
name="username"
placeholder="Enter username"
value={username}
onChange={this.handleInputChange}
/>
</div>
<button disabled={this.isDisabled()}>Add</button>
</form>
{this.state.userExists ? (
<p className="error">You cannot add a user that already exists.</p>
) : (
''
)}
</div>
);
}
}
这将更新state.user,以将输入的名称反映为触发事件的输入的更改,使用输入的名称作为属性/键,并使用输入的值作为其值,同时保留其他值。
括号中的语法[名称]是computed property,因此,如果输入的名称是“香蕉”,则相当于设置{ banana: value }
。