声纳给出“预期的赋值或函数调用”消息

Question

I work in NgRx and I receive this error:

'Expected an assignment or function call and instead saw an expression.'

Sonar issue in this.sfForm.get('code')?.[this._mode ? 'disable' : 'enable'](); this.sfForm.get('code')?.[this._mode ? 'disable' : 'enable'](); .

I don't understand the message from the Sonar, and what to fix here. I need some help to understand the code and resolve the issue.

<mat-form-field [formGroup]="sfForm">
  <input Input
         matInput
         (keydown.enter)="search($event.target.value)"
         [type]="''"
         formControlName="code"
         required>
</mat-form-field>

sfForm: FormGroup;
private _mode: boolean = true;
      
public set scanMode(value: boolean) {
  this._mode = value;
  this.sfForm.get('code')?.[this._mode ? 'disable' : 'enable']();
}

Answer 1

Here's a breakdown of that line:

this.sfForm.get('code') // get by the key "code"
?.                      // if `undefined` or `null`, stop here (see #1 below)
[                       // else, get prop by expression in [square brackets]
    this._mode ?        // if this._mode is truthy...
        'disable'       // that prop is 'disable'
        : 'enable'      // else, that prop is 'enable'
]                       // (see #2 below)
()                      // call the function identified by that prop (with 0 args)

• #1: Explanation of ?.
• #2: Explanation of condition ? val1 : val2 condition ? val1 : val2

---

In more verbose code, it might look like this:

const code = this.sfForm.get('code')

if (code !== null && typeof code !== 'undefined') {
    let modeFunction

    if (this._mode) {
        modeFunction = code.disable
    } else {
        modeFunction = code.enable
    }

    modeFunction()
}

Answer 2

If you mean to assign the labels, you cannot do that in this way. when you do

object[field]

like you did, you cannot assign values.

What you can do, is something like this :

this.sfForm.get('code')?.[this._mode] = this.sfForm.get('code')?.[this._mode] ? 'disable' : 'enable'

or in a shorter way if you want to put the field in a variable.

Also, note that you cannot call to functions inside of the '?' assigns, but only use statements.