Delegate implementing each method of JavaScript

There are many confusing keywords in C #, such as Delegate,func, action, and predicate. Func, action and predicate are essentially delegate, look at the delegate concept below.

1 Delegate Concept

Delegate is essentially a pointer to a function that points to a different function, as long as the signature of the function is consistent with the proxy.

2 Delegate Applications

In fact, Func, Action, predicate and so are all delegate, just special delegate only. The ingenious application of delegate can greatly simplify code and increase flexibility. Here is a piece of JavaScript code, JS often use the array of each method to iterate over the array and handle it, as follows:

1  var arr = ["One", "one", "one", "three", "four"];       2  $.each (arr, function () {       3     alert (this);       4  });     5//above the results of each output are: One,two,three,four

So how to define an array by delegate in C # each method, you can pass the method to achieve flexible logic processing, static Listex class has a static each method, defined as follows:

1 public static t[] each<t> (t[] source, func<t, t> function) 2 {3  4     t[] ret =new t[source. Length]; 5     int i = 0; 6     foreach (T item in Source) 7     {8         ret[i]=function (item); 9         i++;10     }11     return ret ; 12}

Then we can define a string array and define a delegate as a function parameter to pass in, calling the Listex.each method:

1 var arr =new string[]{"One", "one", "one", "three", "four"};     2 var newarr= listex.each<string> (Arr,delegate (String x) {3     x=x+ "_do"; 4     return x;5});

Of course, you can use expressions to simplify:

1 var newArr2 = listex.each<string> (NEWARR, (string x) + x = x + "_do");

We can also define a where method to filter the array:

1 public static ilist<t> find<t> (ilist<t> source, predicate<t> predicate) 2 {3     list<t > ret = new list<t> (); 4     foreach (T item in Source) 5     {6         if (predicate (item)) 7         {8             ret. ADD (item); 9         }10     }11     return ret;12}13 public static t[] where<t> (t[] source, predicate<t> predicate) 14 {15     ilist<t> List=source. Tolist<t> ();     ilist<t> retlist= find<t> (list, predicate);     Retlist.toarray return <T> (); 18}

The call is as follows:

1 var newArr3 = listex.where<string> (arr, x = x = = "both");

3 Differences Overview

Func is the proxy that must specify the return value;

Action is an agent with a return value of void;

predicate is a proxy with a return value of bool;

Delegate implementing each method of JavaScript