CODEWITHSUNDEEP
classdartdart-mirrors
george koller
george koller

Reputation: 3941

How to tell if an object is an instance of a class

How can I determine whether an object is of a class or not in the Dart language?

I'm looking to do something like the following:

if (someObject.class.toString() == "Num") {
    ...
}

And what is the returned value type? Will it have to be a String?

The mirror library has been up and down and seems to be subject to rapid change right now, as the one thing I did find simply did not work as shown.

Upvotes: 44

Views: 30012

Answers (3)

Vadim Tsushko
Vadim Tsushko

Reputation: 1516

Recently Object got the runtimeType getter. So now, we may not only compare type of object with another type, but actually get the class name of an object.

As in:

myObject.runtimeType.toString()

Furthermore, in the current version of Dart, you can skip the toString operation and directly compare runtimeType of object with target type:

myObject.runtimeType == int

or

myObject.runtimeType == Animal

Upvotes: 57

Martinho Mussamba
Martinho Mussamba

Reputation: 467

Here is a simple explanation with a solution.

You have:

Object obj =t1;
where t1 is an object of class T.

And you have other object T called t.

T t = new T();

How to check if obj is the same type of t ?

Solution:

if(obj is t)
     print('obj is typeof t')
   else print('obj is not typeof t')

Upvotes: 0

Eliran Malka
Eliran Malka

Reputation: 16263

  • By using the is and is! operators, like this:

    if (someObject is T)

    From the documentation:

    The is and is! operators are handy for checking types. The result of obj is T is true if obj implements the interface specified by T. For example, obj is Object is always true.

  • Using the Mirrors API (see this example):

    Expect.equals('T', someObject.simpleName)

Upvotes: 56

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