Basic Game Objects - Learning C# by Programming Games - page 93

public void HandleInput()
{
dosomething...
}
Instead of a type like float or bool , the keyword void is written in front of the method
name. void means that the method does not have a return value , meaning that we
cannot store the outcome of this method in a variable. For example, the following
line would result in a compiler error:
float oops = HandleInput();
Also, because this method does not have a return value, we do not need to use the
return keyword inside the body of the method (although it can sometimes be useful,
as we will see). You will notice that whenever a method with no return value is
called, it has no result that can be stored in a variable and whenever a method does
have a return value, this value is used in some way. We can use the value to store it
in a variable, like in this example:
currentMouseState = Mouse.GetState();
The method GetState in the Mouse class has a return value of type MouseState ,sowe
can store it in a member variable of the same type. The following example shows
the calling of two methods neither of which has a return value:
GraphicsDevice.Clear(Color.White);
spriteBatch.Begin();
A return value does not necessarily have to be stored in a variable. We can also
directly use it in an if -instruction, like we do in the HandleInput method:
if (currentKeyboardState.IsKeyDown(Keys.R) &&
previousKeyboardState.IsKeyUp(Keys.R))
currentColor = colorRed;
Here, the IsKeyDown and IsKeyUp methods return a value of type bool . The difference
between things that have a value and things that do not have a value is something
we have seen before: it is the same difference we saw between instructions (which
do not have a value) and expressions which do have a value. So, this means that
IsKeyDown(Keys.K) is an expression , whereas HandleInput(); is an instruction . A sec-
ond difference between these two things is that expressions never end with a semi-
colon, and instructions always end with a semicolon, except if the instruction is a
block.