Why do nested if statements act differently than the && operator?

Questions & Answers
1

I’m following a beginner Unity course, and the instructor used two nested if statements within a method for jumping logic, as so:

//takes care of jumping logic
    private void JumpHandler()
    {
        //store jump input (Jump axis = up/down axis)
        float jAxis = Input.GetAxis("Jump");

        //if the key has been pressed
        if(jAxis > 0)
        {
            if(!pressedJump)
            {
                pressedJump = true;

                //jumping vector
                Vector3 jumpVector = new Vector3(0, jAxis * jumpForce, 0);

                //apply force to rigid body
                rb.AddForce(jumpVector, ForceMode.VelocityChange);
            }
        }
        else
        {
            pressedJump = false;
        }
    }

As I wrote along, I went with:

if(jAxis > 0 && !pressedJump)

as opposed to the instructor’s two nested if statements.

For some reason, the two approaches produce different results. The nested if statements cause it to function as wanted, wherein the player hits the spacebar and a vertical force is applied in a uniform way, regardless of how long the spacebar was pressed, the player gameobject jumps to the same height. However, my && statement always reads true as long as the spacebar is held down, causing the player gameobject to fly to the stars. What am I missing here? What’s going on?

2

It has to do with the else statement. Let’s take your two conditions “jAxis > 0” and “!pressedJump” and just make them “a” and “b” to make things simple. Compare the two situations below. Note how the first statement/comment in the if block(s) has the same logic, but the else is different between the two!

if (a)
{
    if (b) 
    {
         // this will happen if a and b are true
    }
}
else
{
    // this will happen if a is not true
}
-----------------------------------------------------------
if (a && b)
{
    // this will happen if a and b are true
}
else
{
    // this will happen if a is not true OR if b is not true
}