Constructors in dart [duplicate]

Answer 1

You have used named optional arguemnts but your constructor accept postional optional parameter.

named optional parameter {}:

1. Use to omit/avoid arguments and for readability.
2. argument position doesnt matter since refer using name.
3. Since you can avoid the argument, to denote that this argument is required use @required. Most of the time this annotation use to say this is cannot avoid(like a notice).

---

const Category({
    @required this.name,
    @required this.icon,
    @required this.color
  }) : assert(name != null),
      assert(icon != null),
      assert(color != null);

//Category(name: _categoryName, icon: _categoryIcon, color: _categoryColor),

positional optional parameter []:

1. Also use to avoid or omit args.
2. Cannot mention name because of that no readability(as a example for boolean params).
3. Argument position matters.
4. No need of @required because we must provide args.

---

const Category(
    this.name,
    this.icon,
    this.color
  ) : assert(name != null),
      assert(icon != null),
      assert(color != null);

//Category(_categoryName, _categoryIcon, _categoryColor),

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