1/1
What is the difference between final and const?
A constant variable must be initialized at the time of declaration. It's a compile-time constant. A final variable can be initialized later, but only once when the first time it’s used.
What is the difference between final and const?
A constant variable must be initialized at the time of declaration. It's a compile-time constant. A final variable can be initialized later, but only once when the first time it’s used.
1/2
void main() {
final int x;
const int y = 1;
x = 8; // ok
y = 2; // error: Constant variables can't be assigned a value.
x = 9; // error: The final variable 'a' can only be set once.
}
void main() {
final int x;
const int y = 1;
x = 8; // ok
y = 2; // error: Constant variables can't be assigned a value.
x = 9; // error: The final variable 'a' can only be set once.
}
2/1
Const is used to create constant values and to declare constructors by which immutable values are created. This allows any variable to have an immutable value.
Const is used to create constant values and to declare constructors by which immutable values are created. This allows any variable to have an immutable value.
2/2
var one = const [];
one = const [1, 2, 3]; // ok
one[0] = 4; //Unsupported operation: Cannot modify an unmodifiable list
final two = const [];
two = const [10, 3, 23]; // error
const three = [];
three = const [10, 3, 23]; // error
var one = const [];
one = const [1, 2, 3]; // ok
one[0] = 4; //Unsupported operation: Cannot modify an unmodifiable list
final two = const [];
two = const [10, 3, 23]; // error
const three = [];
three = const [10, 3, 23]; // error
3/1
The late was added in Dart 2.12 and has now two uses:
1. To declare a variable that doesn't store a null value, which is initialized after it is declared;
2. For lazy variable initialization.
The late was added in Dart 2.12 and has now two uses:
1. To declare a variable that doesn't store a null value, which is initialized after it is declared;
2. For lazy variable initialization.
3/2
What is the difference between final and late?
Modifier final cannot be declared at the top level of the code. At the same time, variables declared with one of these modifiers must be initialized before they are used. Otherwise, an exception will be thrown.
What is the difference between final and late?
Modifier final cannot be declared at the top level of the code. At the same time, variables declared with one of these modifiers must be initialized before they are used. Otherwise, an exception will be thrown.
3/3
late String lateName;
// final int finalName; // error
void main() {
final int finalName; // ok
// print(lateName); //error
// LateInitializationError: Field 'lateName' has not been initialized
lateName = '#Flutter';
print(lateName); // ok
}
late String lateName;
// final int finalName; // error
void main() {
final int finalName; // ok
// print(lateName); //error
// LateInitializationError: Field 'lateName' has not been initialized
lateName = '#Flutter';
print(lateName); // ok
}
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