如何检查RxJS Observable在Angular2中是否包含字符串?
我是Angular2和Observable的新手，我想检查类型为Observable<string[]>的Observable getRoles是否包含字符串.
I am new to Angular2 and Observable, I want to check if a Observable getRoles which is of type Observable<string[]> contains a string.
public hasRole(name: string): boolean {
// getRoles is of type Observable<string[]>
let getRoles = this.tokenService.getTokenInformation().map(element => element.roles);
if (/* check if name is inside of getRoles */) {
return true;
}
return false;
}
可观察对象是异步的，因此您不能使用let getRoles = ...map(...). map() 方法不是在数组上执行，但在总是异步的Observable上执行.
Observables are asynchronous so you can't use let getRoles = ...map(...). The map() method is not executed on an array but on an Observable which is always asynchronous.
所以正确的方法是(我没有测试这段代码):
So proper way to do it could be (I didn't test this code):
public hasRole(name: string): Observable {
return this.tokenService.getTokenInformation()
.map(element => element.roles)
.first(roles => roles.indexOf(name) !== -1);
}
操作员 first() 当源完成时(当我们迭代所有角色时)未找到匹配的元素时，将发出错误.
Operator first() emits an error when no matching element was found when the source completed (when we iterated all roles).
然后使用这种方法，例如:
Then use this method like:
hasRole('my-role').subscribe(
role => console.log("has role"),
error => console.log("doesn't have role"),
)
这会将所有内容转换为仅true或false值.请参阅doc中的first()运算符，这些参数是什么.然后，我使用map()强制将所有内容都转换为布尔值.
This converts everything to only true or false values. See doc for first() operator what are these argument. Then I used map() to force convert everything into boolean.
public hasRole(name: string): Observable {
return this.tokenService.getTokenInformation()
.map(element => element.roles)
.first(roles => roles.indexOf(name) !== -1, undefined, false)
.map(val => !!val);
}