dynamic

Learn the dynamic type and runtime type checking.

The dynamic type

dynamic is a flexible type that can hold any value. When you make a variable dynamic, Dart leaves type checks to runtime.

For example dynamic x = 5; then x = 'text'; is valid. Because dynamic accepts any type.

This flexibility is not risk-free: type errors only appear when the program runs. So use dynamic carefully; prefer var or explicit types when possible.

The is operator

The is operator checks what type a variable has at runtime. x is int returns true if x is an int.

It is especially used with dynamic variables; their type is not known in advance. You check with is first, then use it safely.

Example: dynamic x = 5; if (x is int) { print('integer'); }. This gives runtime type safety.

Exercise dynamic and is

Declare dynamic x = 5;. Check with if (x is int) and print print('int').

Show example solution

void main() {
  dynamic x = 5;
  if (x is int) {
    print('int');
  }
}

Test yourself

Flexible type
```
____ x = 5;
```
Show answer
```
dynamic x = 5;
```
What is the difference between dynamic and var?
- They are exactly the same
- dynamic is faster
- var is safer
- in dynamic the type can change later
Show answer

in dynamic the type can change later — In dynamic the type can change at runtime; in var it cannot.
dynamic concepts

dynamic

Flexible type
is

Type check
var

Inference
int

Integer

Next lesson: Summary - Data types

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