Print detailed structure / type information of a variable's value

Question

I wonder, if a dart or flutter method exists, which returns complete type information about the structure of a variable's value as a string.

E.g., if some print( someValue.toString() ); emits this

  {"user":"userName","state":"valid"}

I don't know if it is a Map or a String.

But how do I get a string, which describes a variable's value / structure?

Something, that's like PHP's print_r(), which print stuff like this:

Array
(
    [a] => Apfel
    [b] => Banane
    [c] => Array
        (
            [0] => x
            [1] => y
            [2] => z
        )
)

creativecreatorormaybenot · Accepted Answer · 2018-07-25T22:19:50.360

1

There is nothing like print_r() available natively in Dart.
However, it would be possible to use the following functionalities to build e.g. a function like print_r() from PHP.

You can evaluate the type of someValue using runtimeType.

String someValueType = someValue.runtimeType.toString();
String someValueString = someValue.toString();

If you want to compare, you can also use is. More on that here.
Dart is a strongly typed language, which means that you could also enforce types (List a; String b), which makes a function like print_r() redundant for Dart.

edited Jul 25 '18 at 22:19

answered Jul 25 '18 at 01:37

creativecreatorormaybenot

114,516
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1

I'm aware of these aspects. Add a line to text, that states that no print_r() like method exists. And I'm going to accept your insert. – SteAp Jul 25 '18 at 15:28
@SteAp I added that. I think that Dart does not need anything like `print_r()` because of its typing. – creativecreatorormaybenot Jul 25 '18 at 22:20

score 1 · Answer 2 · edited Jul 26 '18 at 16:31

If it is about server-side code you can use reflection to create a function that produces such an output for every value.

If it is about your own classes, you can implement toString() to make the objects render themselves this way when they are printed

class Person {
  Foo(this.firstName, this.lastName);

  String firstName;
  String lastName;

  @override
  String toString() => '''
firstName: $firstName
lastName: $lastName
''';      
}

print(new Person('John', 'Doe'));

score 0 · Answer 3 · answered Sep 04 '22 at 21:41

0

Best way to do is

print(”$someValue“);

It will return a structured string which similar to JSON.

answered Sep 04 '22 at 21:41

Poohspear

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Print detailed structure / type information of a variable's value

3 Answers3