How to set value of input field with NgIf in Angular 4

Question

I am pretty new with Angular 4 and I have probably basic question for someone who is a bit more experienced than me.

I have input field which value needs to be populated when object user exists. So basically I need php function isset() in angular 4.

I tried like this but it is not working.

<input class="form-control" type="text"  value="{{ !!user.firstname ? user.firstname : null }}" id="firstname">

Any help would be appreciated.

Tnx

Answer 1

您应该在输入中使用[[ngModel）]并使用elvis运算符检查用户是否存在或使用*ngIf

<input class="form-control" type="text"  [(ngModel)]=user?.firstName id="firstname">

Answer 2

尝试这个 ：

<input class="form-control" type="text" [value]="user.firstname ? user.firstname : null"  name="firstname" id="firstname">