Operator ' ' cannot be called on 'String?' because it is potentially null. In Fl-CodePudding

I am trying to make an app which takes names then validates it. I got which says : The operator ' ' can't be unconditionally invoked because the receiver can be 'null'. I tried to write ' if (value != null), but then i got another error.

Expanded(
    child: ListView.builder(
        itemCount: animeler.length,
        itemBuilder: (BuildContext context, int index) {

            return ListTile(title:
                Text(animeler[index].animeName  
                " : "  
                animeler[index].animePoint.toString()),
                
        })),

This is the class :

class Animes {
  String? animeName = "";
  double animePoint = 0;
  String animeLover = "";


  Animes(String animeName, double animePoint, String animeLover) {
    this.animeName = animeName;
    this.animePoint = animePoint;
    this.animeLover = animeLover;
  }

  
}

This is where i got the anime name. I have a variable anime.

  Widget buildFirstNameField()
  {
    return TextFormField(
      decoration: InputDecoration(labelText: "Anime name", hintText: "Death Note"),
      validator: vallval,
      onSaved: (String? value)
      {
        anime.animeName = value;

      },
    );
  }
}

i call the 'buildFirstNameField' function in:

body: Container(
  margin: EdgeInsets.all(20.0),
  child: Form(
    child: Column(
      children: <Widget>[
        buildFirstNameField(),

CodePudding user response：

animeName is a nullable String, so it is possible to get null, you can provide default value on null case like myNullableVariable ?? defaultValue

But you can use String format here,

 Text("${animeler[index].animeName??""} : ${animeler[index].animePoint.toString()}")

CodePudding user response：

because you already set a default value in your model class you can use ! and by that you tell to compiler that you are sure that your variable(animeName) isn't null:

ListTile(
   title: Text(animeler[index].animeName!  
         " : "   animeler[index].animePoint.toString()),
)

This is because you set String? animeName as nullable variable in your model.