var and type
- Dart course
- Beginner
- Lesson 7/116
- 4 min
Learn to declare variables with var and explicit types.
var and explicit type
In Dart you declare a variable in two ways: with the var keyword or with an explicit type. For example var age = 25; and int age = 25; do the same thing.
When you use var, Dart infers the type from the value on the right. So var x = 5; makes x an int, not dynamic.
Writing the explicit type can make code more readable; in team work seeing the type helps. Both are valid; be consistent.
Type inference
Type inference means the compiler finds the type for you. When you write var name = 'Alex';, Dart knows name is a String.
Once the type is set, it does not change. So var x = 5; followed by x = 'text'; is an error; x is now an int.
Writing the explicit type can be clearer in the long run. But for short scripts var is faster. Both are accepted in Dart culture.
Practice Declare four types
Inside void main(), declare one variable of each type: int, double, String and bool. Set the values to 25, 9.99, Alex and true respectively. Then print each one with print.
Starter code
// Declare four variables and print themSample solution
void main() {
int age = 25;
double price = 9.99;
String name = 'Alex';
bool active = true;
print(age);
print(price);
print(name);
print(active);
}Expected output
25 9.99 Alex true
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 When you write var x = 5;, what is the type of x?
- dynamic
- int Correct answer
- var
- object
Explanation: Dart infers int from the value 5.
2 Integer type
____ age = 25;int age = 25;Explanation: int is the 64-bit integer type.
3 Match the types
| Term | Meaning |
|---|---|
int |
Integer |
double |
Floating-point |
String |
Text |
bool |
Boolean |