角4无限阵列循环

Question

我想使用* ngFor并重复我的数组元素myltiple次。像这样：

在组件中：

mesViv = ((fech_act//10000)%100) - ((fec_nac//10000)%100)
mesViv = ((25072017//10000)%100) - ((11101982//10000)%100)
mesViv = (2507%100) - (1110%100)
mesViv = (7) - (10)
mesViv = -3

在模板中：

import datetime

def numerical_date_to_date(dtint):
    # Factor out conversion from weird int-based format to datetime.date
    daymon, years = divmod(dtint, 10000)
    days, months = divmod(daymon, 100)
    return datetime.date(years, months, days)

def min_vivido(fech_act, fec_nac):
    diff = numerical_date_to_date(fech_act) - numerical_date_to_date(fec_nac)
    horas_dias = diff.days * 24
    min_dias = horas_dias * 60
    return min_dias, horas_dias, diff.days

我想在渲染中看到类似的东西：

a，b，c，d，e

点击＆＃39; a＆＃39;：

d，e，a，b，c

点击＆＃39; e＆＃39;：

c，d，e，a，b

有什么想法吗？ :) 谢谢你的帮助！

Answer 1

试试这会解决您的问题

 <div *ngFor="let letter of letters" (click)="myMethod(letter)">{{letter}}
</div>


myMethod(selectedLetter){
    let postLen = 3; // configurable
    let i=0, len =str1.length;
    let foundFlag = false;
    let arr1 = [], arr2 = [], arr3 = [];
    for(;i<len;i++){
         if(str1[i] == selectedLetter){
             for(k=0;k<postLen && (i+k)< len ; k++){
                arr1.push(str1[i+k]);
                i++;
             }
             foundFlag = true;
         }else if(!foundFlag){
                arr2.push(str1[i]);
         }else{
                arr3.push(str1[i]);
         }

    }

    this.letters = arr3.concat(arr2);
    this.letters = this.letters.concat(arr1);   

}

Answer 2

只需使用ngIf的两个列表：第一个列表会在currentLetter或currentLetter之前呈现字母，而第二个列表会在currentLetter之后呈现字母。

<ng-container *ngFor="let letter of letters; index as i">
  <button *ngIf="i>=letters.indexOf(currentLetter)" (click)="currentLetter = letter">{{letter}}</button>
</ng-container>
<ng-container *ngFor="let letter of letters; index as i">
  <button *ngIf="i<letters.indexOf(currentLetter)" (click)="currentLetter = letter">{{letter}}</button>
</ng-container>