Question

我只需要过滤categoria为a的那些对象。有什么办法可以使用ngFor做到这一点？

service.ts：

productos: Producto[] = [
  {id:'01', categoria:'a', titulo:'title1'},
  {id:'02', categoria:'b', titulo:'title2'},
  {id:'03', categoria:'a', titulo:'title3'},
  {id:'04', categoria:'c', titulo:'title4'},
  {id:'05', categoria:'c', titulo:'title5'}
]

getProductos() {
   return of(this.productos);
}

component.ts：

ngOnInit() {
  this.productos$ = this.ps.getProductos();
}

component.html：

<div *ngFor="let producto of productos$ | async">
  {{ producto.titulo}}
</div>

Answer 1

您可以使用管道（请参阅Vinit链接）或使用过滤器

import random
import sys

K_SIZE = 1000

class Generator:
    def __init__(self,low=4,high=10):
        self.table = {i:chr(i) for i in range(33,127)}
        self.low = low
        self.high = high


    def create_n_bytes(self,total_bytes):
        bytes_created = 0
        """Hack at the moment, this condition will fail only after more than n bytes are 
        written """
        while bytes_created < total_bytes:
            bytes_to_create = random.randint(self.low,self.high)
            bytes_created = bytes_created+bytes_to_create+1
            word=[""]*bytes_to_create
            for i in range(bytes_to_create):
                word[i] = self.table[random.randint(33,126)]
            text = "".join(word)
            #print(str(hash(text))+"\t"+text)
            print(text)

def get_file_size_from_command_line():
    size = sys.argv[1]
    return size

def get_min_word_len_from_command_line():
    if len(sys.argv) > 2:
        low = sys.argv[2]
        return int(low)

def get_max_word_len_from_command_line():
    if len(sys.argv) > 3:
        high = sys.argv[3]
        return int(high)

def get_file_size_in_bytes(size):
    multiplier = 1
    size_unit = size[-1]

    if size_unit == 'M' or size_unit == 'm':
        multiplier = K_SIZE*K_SIZE
    elif size_unit == 'K' or size_unit == 'k':
        multiplier = K_SIZE
    elif size_unit == 'G' or size_unit == 'g':
        multiplier = K_SIZE*K_SIZE*K_SIZE
    elif size_unit in ('0','1','2','3','4','5','6','7','8','9'):
        multiplier = 1
    else:
        print("invalid size")
        exit()

    total_bytes = 0
    if multiplier == 1:
        total_bytes = int(size)
    else:
        total_bytes = multiplier*int(size[:len(size)-1])

    return total_bytes


def main():
    if len(sys.argv) == 2:
        gen = Generator()
    elif len(sys.argv) == 3:
        gen = Generator(get_min_word_len_from_command_line())
    elif len(sys.argv) == 4:
        gen = Generator(get_min_word_len_from_command_line(),get_max_word_len_from_command_line())
    file_size = get_file_size_in_bytes(get_file_size_from_command_line())
    gen.create_n_bytes(file_size)

if __name__== "__main__":
    main()

Answer 2

您可以使用过滤器运算符来做到这一点。

ngOnInit() {
     this.productos$ = this.ps.getProductos().pipe(filter(el => el.categoria == 'a'));
}

从数组对象过滤* ngFor

2 个答案: