CODEWITHSUNDEEP
dartlambdaparameters
munir.aygun
munir.aygun

Reputation: 442

Lambda Expression as a function parameter in Dart Language

I am trying to build a class to making some operations in mathematical sequences in Dart . And I am expecting a sequence as a lambda expression or function . I got confused when I try to build constructor of class . What should I write for parameters and data types ?

Sample lambda expression :

int sequence(int n) => 7+5*(n-1);

Sample function :

int fib(int n) {
  if ((n == 1) || (n == 2)) {
    return 1;
  } else {
    return fib(n - 1) + fib(n - 2);
  }
}

How can I give that lambda expression and function as a parameter to another function ?

Upvotes: 1

Views: 3339

Answers (1)

julemand101
julemand101

Reputation: 31219

So the type of your two methods are int Function(int) which means it takes one int as a parameter and outputs a int.

There are basically two ways to do it. One is to explicit type that type as a parameter type like:

int sequence(int n) => 7 + 5 * (n - 1);

int generate1(int Function(int) function, int input) => function(input);

void main() {
  print(generate1(sequence, 5)); // 27
}

Another way is to define a typedef which will be a shorthand for your type:

int fib(int n) {
  if ((n == 1) || (n == 2)) {
    return 1;
  } else {
    return fib(n - 1) + fib(n - 2);
  }
}

typedef SomeFunction = int Function(int n);
int generate2(SomeFunction function, int input) => function(input);

void main() {
  print(generate2(fib, 5));      // 5
}

The typedef can be easier if you have more complicated types you are reusing for multiple methods.

Upvotes: 4

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