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# Conditionals

If we want to execute a chunk of code only when a condition is met, then in Swift, we can use **if, else if, and else** **statements**. Let’s take a look at the following example:

```swift
var a = 0
if a == 0 {
    print("Zero")
} else {
    print("Not Zero")
}
```

When using conditionals, we must provide a condition which is an expression that evaluates to `true` or `false`. To enclose a block of code in Swift, we use curly brackets (`{` and `}`). In the example above, the expression `a == 0` evaluates to `true` so the block of code containing `print("Zero")` will be executed.

<figure><img src="/files/iiTRX8WNecXmvmbNkYvN" alt=""><figcaption></figcaption></figure>

Now, what if `a == 0` evaluates to `false`? In that case, Swift will read for the next condition, if any. Because the next statement is an `else` statement, there is no condition to check so this block of code will be executed.

<figure><img src="/files/c23IQJJJFFPokfAeseEt" alt=""><figcaption></figcaption></figure>

Sometimes, we want to check for multiple conditions? In that case, there is more than one option:

1. Use the `&&` (and) or `||` (or) operators
2. Use an `else if` statement

Let’s take a look at the second option.

```swift
var a = -6
if a < 0 {
    print("Negative")
} else if a % 2 == 0 {
    print("Even")
} else {
    print("Not even or negative")
}
```

First, the expression `a < 0` is evaluated. Since `-6 < 0` evaluates to `true`, Swift executes the block of code containing `print("Negative")`. Now, since the next statement is an else if statement, it will not be executed. The reason is because this else if statement is connected to an if statement. Since the first if statement evaluated to `true`, Swift will not check any other statements that are connected.

<figure><img src="/files/IhwzHlnlqLz7mQTt5moK" alt=""><figcaption></figcaption></figure>

Now, if we were to change the else if statement to an if statement, Swift will check this statement because it is no longer connected to the first if statement.

<figure><img src="/files/VkDUBdZRL8trVgWBwP1N" alt=""><figcaption></figcaption></figure>

Because both conditions are met and they are not linked together, `"Negative"` and `"Even"` will both be printed.

### Guard Statement

Sometimes we want to exit our code execution early on for efficiency purposes. This is where the **guard statement** comes in. A guard statement is similar to an if statement except an if statement runs when the condition is `true` while a guard statement runs when the condition is `false`. We can think of a guard statement as using an if statement with a “not equals” (`!=`) or not” (`!`) operator.

The format for a guard statement is as follows:

```swift
guard condition else {
    // block of code
    // control statement: return, break, continue, or throw
}
```

`condition` is an expression that evaluates to `true` or `false`. If `true`, then the block of code is not executed. If `false`, then the block of code is executed. This is the exact opposite of an **if** statement.


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