如何在 angular 中將項目添加到我的 FormArray？

Question

我正在嘗試向我的 FormArray 添加一些項目，但我總是得到：core.js:6241 ERROR TypeError: Cannot read property 'push' of null。

我可以使用我的get answersFormArray() 將 itens添加到測試數組中，但我無法添加到字母和文本表單數組中。 我嘗試調用letterFormArray.push(value here)但給了我同樣的錯誤。

       this.userForm = this.fb.group({
      fname: ['', [Validators.required]],
      lname: ['', [Validators.required]],
      email: ['', [Validators.email, Validators.required]],
      facility: ['', [Validators.required]],
      testCode: ['', [Validators.required]],
      date: [''],
      test: this.fb.group({
        name: [''],
        id: [''],
        position: [''],
        scored: [''],
        wrong: [''],
        duration: [''],
/*         answers: this.fb.array([
          this.fb.group({
            num:'',
            letter: this.fb.array([]),
            text: this.fb.array([]),
            userLetter: this.fb.array([]),
            userText: this.fb.array([]),
          })
        ])
      }), */
        answers: this.fb.group({
          user: this.fb.array([
            this.fb.group({
              num:'',
              letter: this.fb.array([]),
              text: this.fb.array([]),
            })
          ]),
          teste: this.fb.array([
            this.fb.group({
              num:'',
              letter: this.fb.array([]),
              text: this.fb.array([]),
            })])
        })
      })
    })

我正在嘗試將 itens 添加到字母和文本FormArray。

  get answersFormArray() {
    //return this.userForm.get('test.answers') as FormArray //Option 1
    return this.userForm.get('test.answers.teste') as FormArray
  }

  get letterFormArray() {
    return this.userForm.get('test.answers.teste.letter') as FormArray;
  }
  get textFormArray() {
    return this.userForm.get('test.answers.teste.text') as FormArray;
  }


getTestCorrectAnswers() {
    for(let i = 0; i < this.current_quest.length; i++) {
      const answ = this.fb.group({
        numb: i+1,
        letter: this.fb.array([]),
        text: this.fb.array([])
      })
      for(let z = 0; z < this.current_quest[i].alternatives.length; z++) {
      const alter = this.fb.control("");
        //objective
        if(this.current_quest[i].type === "objective") {
          if(this.current_quest[i].single_or_multi === "single") {
            if(this.current_quest[i].alternatives[z].correct == true) {
              this.textFormArray.push(this.fb.control(this.current_quest[i].alternatives[z].text));
              this.letterFormArray.push(this.fb.control(this.current_quest[i].alternatives[z].letter));
              console.log("Objetiva com uma única alternativa --> " + this.current_quest[i].alternatives[z].text);
            }
          }
          else {
            if(this.current_quest[i].alternatives[z].correct == true) {
              
              console.log("Objetiva com várias alternativas --> " + this.current_quest[i].alternatives[z].text);
            }
          }

        }
        //Subjective
        else {
          if(this.current_quest[i].alternatives.length >= 1) {
            console.log("Subjetiva com chave de resposta --> " + this.current_quest[i].alternatives[z].text);
          }
          else if(!this.current_quest[i].alternatives.length){
            console.log("Subjetiva sem chave de resposta --> ");
          }
        }
        
      }
      this.answersFormArray.push(answ);
    }
  }

這是我正在創建的 object 的示例...

teste: [
        {
          "numb": 1,
          "letter": ["a", "b"],
          "text": ["red", "yellow"]
        },
        {
          "numb": 2,
          "letter": ["a"],
          "text": ["black"]
        }
]

Answer 1

letter和text是 FormArray 嵌套到另一個 FormArray 中的。 由於 FormArray 基本上是一個數組，因此您需要定位填充到其中的 FromGroup 的索引。

get letterFormArray(index: number) {
    return this.userForm.get('test.answers.teste[index].letter') as FormArray;
  }

Answer 2

安德烈，你通常有

get users()
{
  return this.userForm.get('test.answer.users') as FormArray
}
get teste()
{
  return this.userForm.get('test.answer.teste') as FormArray
}

要到達 FormArray 的元素，您需要一個“索引”，並且您不能使用 getter，請參閱 getLetter 一起，而不是獲取 Letter，另請參閱我們如何使用之前定義的 getter

getLetter(index){
    return this.answer.at(index).letter as FormArray
}
getTest(index){
    return this.answer.at(index).test as FormArray
}

現在你可以做

  this.getLetter(index.push(...);
  //and
  this.getTest(index.push(...);