CODEWITHSUNDEEP
c#
Kaoru
Kaoru

Reputation: 2883

What does this variable mean?

i saw this in the internet, and i couldn't think what is this about:

they created the boolean which is named obstacles and set it to false.

   public bool obstacles = false;

But, what is this line about:

    obstacles = obstacles ? false : true;

    if (obstacles)
    {
        transform.renderer.material.color = new Color(.5f, .5f, 0.0f);
    }

    else
    {
        transform.renderer.material.color = Color.white;
    }

I know the if and else function, when there is an obstacles, turn the material to the assigned color, or if there is not an obstacles, turn the material into white color. But, what is this line about: obstacles = obstacles ? false : true;

Thanks.. Sorry for this newbie question.

Upvotes: 0

Views: 141

Answers (5)

Rahul Tripathi
Rahul Tripathi

Reputation: 172518

?: This is called the ternary operator

The conditional operator (?:) returns one of two values depending on the value of a Boolean expression. Following is the syntax for the conditional operator.

condition ? first_expression : second_expression;

Remarks

The condition must evaluate to true or false. If condition is true, first_expression is evaluated and becomes the result. If condition is false, second_expression is evaluated and becomes the result. Only one of the two expressions is evaluated.

Either the type of first_expression and second_expression must be the same, or an implicit conversion must exist from one type to the other.

The example from MSDN makes it clear:

int input = Convert.ToInt32(Console.ReadLine());
string classify;

// if-else construction.
if (input < 0)
    classify = "negative";
else
    classify = "positive";

// ?: conditional operator.
classify = (input < 0) ? "negative" : "positive";

As Steeve correctly pointed out, you may try like this using a if else statement to what you want to accomplish:

if (!obstacles)
{
    transform.renderer.material.color = new Color(.5f, .5f, 0.0f);
    obstacles = true;
}

else
{
    transform.renderer.material.color = Color.white;
    obstacles = false;
}

Upvotes: 5

Steve
Steve

Reputation: 216313

All the answers explain what is a ternary operator and they are all right, but everyone fails to note the elephant in the room. Why not to remove the ternary operator and write the code above as

if (!obstacles)
{
    // Enter the if with obstacles = false, but execute the code for true then flip obstacles
    transform.renderer.material.color = new Color(.5f, .5f, 0.0f);
    obstacles = true;
}

else
{
    // Enter the else with obstacles = true, but execute the code for false then flip obstacles
    transform.renderer.material.color = Color.white;
    obstacles = false;
}

Upvotes: 4

Sudhakar Tillapudi
Sudhakar Tillapudi

Reputation: 26209

?: called ternary operator

functionality :

var value= (Condition/Expression)? value1 :value2;

means 

if(Condition== true)
value=value1;
else
value=value2;

Your code:

public static bool obstacles = true;
bool value=(obstacles = obstacles) ? false : true;

output: value=false

your expression => (obstacles = obstacles) always evaluates to whatever value is there in obstacles so here it is true. hence first value here false will be assigned to your variable value.

Upvotes: 1

nullop
nullop

Reputation: 554

This line basically "flips" the value of "obstacles" variable to the opposite value. If obstacles is true, it changes it's value to false and vice-versa. So, the author of this code probably is trying to draw something similar to an interleaved pattern here.

Upvotes: 2

Pepe
Pepe

Reputation: 6480

This is the ternary operator. Basically, if condition is true, execute first statement, else execute the second.

condition ? first_expression : second_expression;

http://msdn.microsoft.com/en-us/library/ty67wk28(v=vs.110).aspx

Upvotes: 1

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