Const vs Final in Flutter / Dart

In Flutter, final and const are both used to declare variables that cannot be reassigned.

final variables are evaluated at runtime and can only be set once. They are often used when the value of a variable needs to be determined at runtimes, such as when it is based on user input or the result of a function.

const variables, on the other hand, are evaluated at compile-time and must be known at the time the code is written. They are often used for values that will not change, such as constants or hard-coded values.

Here are some key differences between final and const in Flutter:

• final variables are evaluated at runtime, while const variables are evaluated at compile-time.
• final variables can only be set once, while const variables cannot be set at all.
• final variables can be different for each object, while const variables are the same for all objects.
• final variables are slower to access than const variables, since they are evaluated at runtime.

In general, you should use final variables when you need to set a value at runtime and const variables when you need to use a constant value that is known at compile-time.

Here is an example of how final and const can be used in Flutter:

final int x = 42; // x is a final variable whose value is evaluated at runtime
final int y = calculateValue(); // y is a final variable whose value is determined when it is first accessed

const int a = 42; // a is a const variable whose value is evaluated at compile-time
const int b = calculateValue(); // This will cause an error because calculateValue() is not a compile-time constant

In general, you should use const variables when possible because they are more efficient and can be evaluated at compile time. However, if you need to declare a variable that cannot be reassigned and whose value is not known at compile-time, you can use the final keyword.

Thank you for reading! Cheers!!