Function Block passing in Dart

In Dart, block passing refers to passing a block of code as a parameter to a function or method. There are two main ways to use block passing in Dart:

1. Anonymous functions as parameters:
An anonymous function is a function without a name, and it can be used as a parameter to another function. The syntax for using an anonymous function is:

functionName((parameters) {
  // block of code
});

For example:

void main() {
  var myList = [1, 2, 3, 4, 5];
  var doubled = myList.map((number) => number * 2);
  print(doubled);  // output: (2, 4, 6, 8, 10)
}

In the above example, we are passing an anonymous function to the map() method of the myList object. The anonymous function takes a parameter number and returns the doubled value of the number.

2. Function literals:
Function literals are a shorthand way of writing anonymous functions, and they can also be used as parameters to other functions. The syntax for using a function literal is:

functionName((parameters) => expression);

For example:

void main() {
  var myList = [5, 10, 15, 20];
  var total = myList.fold(0, (sum, number) => sum + number);
  print(total);  // output: 50
}

In the above example, we are passing a function literal to the fold() method of myList. The function literal takes two parameters sum and number, and returns their sum. The fold() method uses this function to calculate the total sum of the elements in myList.

In summary, block passing in Dart gives us the flexibility to pass blocks of code as parameters to functions and methods, allowing us to write more concise and expressive code.