Question

嗨我想用＆＃34; for＆＃34; scala中的map方法。

我该怎么做？

例如，对于每行读取，我想生成一个随机字：

Array[(String, String)] = Array((1,""), (2,""), (3,""), (4,""), (5,""), (6,""), (7,""), (8,""), (9,""), (10,""), (11,""), (12,""), (13,""), (14,""), (15,""), (16,""), (17,""), (18,""), (19,""), (20,""), (21,""), (22,""), (23,""), (24,""), (25,""), (26,""), (27,""), (28,""), (29,""), (30,""), (31,""), (32,""), (33,""), (34,""), (35,""), (36,""), (37,""), (38,""), (39,""), (40,""), (41,""), (42,""), (43,""), (44,""), (45,""), (46,""), (47,""), (48,""), (49,""), (50,""), (51,""), (52,""), (53,""), (54,""), (55,""), (56,""), (57,""), (58,""), (59,""), (60,""), (61,""), (62,""), (63,""), (64,""), (65,""), (66,""), (67,""), (68,""), (69,""), (70,""), (71,""), (72,""), (73,""), (74,""), (75,""), (76,""), (77,""), (78,""), (79,""), (80,""), (81,""), (82,""), (83,""), (84,""), (85,""), (86...

我目前的输出是：

import { Injectable } from '@angular/core';
import { Http, Response, Headers, RequestOptions } from '@angular/http';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
import { Observable } from 'rxjs/Rx';

@Injectable()
export class CartService {
    totalQuantity: Number = 0;

    constructor(private _http: Http) { };

    getCartItems(userId) {
        let headers = new Headers({ 'Authorization': 'JWT ' + localStorage.getItem('currentUserToken') });
        let options = new RequestOptions({ headers: headers });
        return this._http.get('http://localhost:3000/cart/getitem/' + userId, options)
            .map((response: Response) => {
                this.totalQuantity = response.json().totalQuantity;
                return response.json();
            })
            .catch(this._handlerError)
    }

    updateCartItem(item){
        console.log(item);
        let headers = new Headers({ 'Authorization': 'JWT ' + localStorage.getItem('currentUserToken') });
        let options = new RequestOptions({ headers: headers });
        return this._http.post('http://localhost:3000/cart/updateitem/', item, options)
            .map((response: Response) => {
                this.totalQuantity = response.json().totalQuantity;
                return response.json();
            })
            .catch(this._handlerError)
    }

    removeCartItem(item){
        let headers = new Headers({ 'Authorization': 'JWT ' + localStorage.getItem('currentUserToken') });
        let options = new RequestOptions({ headers: headers });
        return this._http.post('http://localhost:3000/cart/deleteitem/', item, options)
            .map((response: Response) => {
                this.totalQuantity = response.json().totalQuantity;
                return response.json();
            })
            .catch(this._handlerError)
    }

    _handlerError(err: any) {
        console.log(err);
        // throw err;
        return Observable.throw(err);
    }
}

我不知道为什么右边是空的。

Answer 1

这里不需要var。这是一个单线

  Seq.fill(len)(chars(rnd.nextInt(51))).mkString

这将通过重复调用len来创建长度为chars(rnd.nextInt(51))的Char序列，然后将其变为字符串。

因此，您将获得以下内容：

import org.apache.spark.rdd.RDD
import scala.util.Random

val chars = ('a' to 'z') ++ ('A' to 'Z')

val rdd = file.map(line => {
  val randomWord = {
    val rnd = new Random
    val len = 4 + rnd.nextInt((6 - 4) + 1)
    Seq.fill(len)(chars(rnd.nextInt(chars.length-1))).mkString
  }
  (line, randomWord)
})

Answer 2

word.concat不会修改word但会返回一个新字符串，您可以将word变为一个变量并为其添加新字符串：

var word = new String
....
for {
    ...
    word += char
    ...
}

使用Scala使用Spark循环到map方法

2 个答案: