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Method Arguments

Name: Method Arguments
Uploaded: 2019-05-28T03:42:16-04:00
Duration: 270 s
Description: We can get our methods to accept arguments using method parameters.

4:30 with Jay McGavren

We can get our methods to accept arguments using method parameters.

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It would be nice to be able to specify how long our Wait method should pause for.
We could do that by passing it an argument. For example, we could pass it the number of milliseconds to wait for: Wait(3000);
But if we try to run that code, we get an error: "No overload for method 'Wait' takes 1 arguments".
In other words, a call to Wait can't accept an argument... yet.
We can get it to accept one using method parameters.
Here's a program that declares an Add method that accepts two parameters, and a Subtract method that also accepts two parameters.
A parameter is a special variable that you declare at the start of a method.
- It's just like declaring a variable; you specify a type and a name for the parameter.
- You can specify multiple parameters by separating them with commas.
Within the method body, you can access the parameter just like you would a variable.
- In the Add method, we print the value of the first parameter, and then print the value of the second parameter.
- Then we print the result of adding first and second together.
When a method takes parameters, you need to provide argument values when calling that method.
- C# sets each parameter variable with the value in the argument.

using System;

class Program
{
    static void Add(double first, double second)
    {
        Console.WriteLine(first);
        Console.WriteLine(second);
        Console.WriteLine(first + second);
    }

    static void Subtract(double first, double second)
    {
        Console.WriteLine(first);
        Console.WriteLine(second);
        Console.WriteLine(first - second);
    }

    static void Main(string[] args)
    {
        Add(3, 5); // => 8
        Add(10.5, 7.2); // => 17.7
        Subtract(9, 3); // => 6
        Subtract(21.3, 7.1); // => 14.2
    }
}

We can update Wait with a parameter, and pass arguments when we call it:

using System;
using System.Threading;

class Program
{

    static void Wait(int delay)
    {
        Console.WriteLine("Waiting...");
        Thread.Sleep(delay);
        Console.WriteLine("Done");
    }

    static void Main(string[] args)
    {
        Wait(1000);
        Wait(3000);
    }

}

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Here is our Wait method from earlier. 0:00

It would be nice to be able to specify how long it should pause for. 0:02

We could do that by passing in an argument. 0:07

For example, we can pass at the number of milliseconds to wait for. 0:09

3,000 milliseconds will cause it to wait for 3 seconds. 0:14

But if we save this code and try to run it, 0:18

We get a compiler error, no overload for method Wait takes 1 arguments. 0:24

In other words, a call to wait can accept an argument. 0:29

We can give it to accept one using method parameters. 0:32

Here's a program that declares an Add method that accepts two parameters and 0:36

then another subtract method that also accepts two parameters. 0:40

A parameter is a special variable that you declare at the start of a method. 0:44

It's just like declaring a variable. 0:48

You specify a type and a name for the parameter. 0:49

You can specify multiple parameters by separating them with commas. 0:53

Within the method body, you can access the parameter just like you would a variable. 0:57

In the Add method, we print the value with the first parameter and 1:01

then print the value of the second parameter. 1:05

Then we print the result of adding the first and second parameter together. 1:07

When a method takes parameters, 1:12

you need to provide argument values when calling that method. 1:13

C# sets each parameter value with the value in the argument. 1:16

So this first argument to Add is going to be the value that the first parameter 1:23

gets set to. 1:28

The second argument in the method call is going to be the value that 1:31

the second parameter gets set to. 1:36

Let's save this and try running it, with dotnet run. 1:38

And you can see that it prints the value of the first parameter, then the value 1:45

of the second parameter, and then the value of adding the two together. 1:49

Let's try adding another column with different arguments. 1:58

So I'll call Add and pass the first argument of 10.5 and 2:01

the second argument of 7.2, let's try saving that. 2:04

And running it. 2:10

And there we are, and our first parameter is set to 10.5. 2:14

Our second parameter to 7.2 and here's the result of adding the two together. 2:18

Let's try calling this subtract method with a first argument of 9 and 2:26

the second argument of 3. 2:30

Let's save this and try running it. 2:32

And here we are at the bottom, our first parameter is set to 9, our second to 3, 2:39

and here's the result of subtracting 3 from 9. 2:44

One last call, let's call Subtract again with different arguments. 2:47

21.3 and 7.1 save this. 2:57

Run it? 3:02

And there's the results of calling Subtract with different arguments. 3:04

Let's take what we've learned and fix our Wait method. 3:09

We want to be able to pass an argument to it with the number of milliseconds that it 3:12

should wait for. 3:16

But right now we're getting an error saying no overload for 3:17

method Wait takes one arguments. 3:20

That's because we haven't set any parameters up in the definition for 3:22

the Wait method. 3:25

Let's go ahead and add one now and see if that fixes it. 3:26

So I'll add an int parameter because this is going to accept an integer and 3:29

we'll name it delay. 3:35

I don't need to make any other changes to the method except to take this hard coded 3:38

3000 millisecond value and replace it with the name of the delay parameter. 3:42

Let me save this and we'll try running it. 3:47

You can see it says waiting, it waits three seconds and then it prints done. 3:53

Let's try adding a call to wait with a different argument and see if it waits for 4:01

a different period of time. 4:04

We'll say wait(1,000) milliseconds, so 1 second. 4:06

Save that. 4:09

Try running it. 4:11

And first, it waits for one second, and prints done. 4:16

Then it waits for three seconds and prints done. 4:18

So by adding a delay parameter to the weight method definition, we were able to 4:21

pass arguments to our calls to wait, saying how long it should wait for. 4:25

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C# Basics

Method Arguments

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