Conditional Structures: How to Use if and switch

Ternary operator

dir = close > open ? 1 : -1
color = close > open ? color.lime : color.red

Nested ternaries read best when each branch is on its own line:

regime =
      close > ta.sma(close, 200) ? "bull"
    : close < ta.sma(close, 200) ? "bear"
    : "neutral"

Both branches must share a type (see Operators).

if statement

if cond
    body
else if cond2
    body2
else
    body3

The if/else if/else chain can be as long as you like.
Blocks are indented; the dedent closes the block.
Any number of else if branches is allowed.

if close > ta.sma(close, 20)
    bgColor = color.new(color.lime, 90)
else if close < ta.sma(close, 20)
    bgColor = color.new(color.red,  90)
else
    bgColor = color.new(color.gray, 90)

`if` as an expression

Assign the result of an if block to a variable — the last statement of the taken branch becomes the value:

score =
    if close > open
        1
    else if close < open
        -1
    else
        0

Branches must share a type.

Nested `if`

Nest as deeply as needed:

if cond1
    if cond2
        innerBody
    else
        otherInner
else
    outer

switch statement

Two forms are supported.

Expression switch

tf = input.string("D", "Timeframe", options=["30", "60", "D", "W"])

bars =
    switch tf
        "30" => 48
        "60" => 24
        "D"  => 1
        "W"  => 5
        => 1               // default (no match)

The subject expression is evaluated once; its value is compared with each arm's match value with ==.
The right side of => is either a single expression or an indented block whose last statement is the value.
An arm with no match (=> …) is the default. Omitting it is allowed; a non-match returns na.

Boolean-chain switch

Omit the subject to use each arm's left side as a condition — the first truthy arm wins:

color =
    switch
        close > open and volume > ta.sma(volume, 20) * 2 => color.lime
        close < open and volume > ta.sma(volume, 20) * 2 => color.red
        close > open => color.new(color.lime, 60)
        close < open => color.new(color.red,  60)
        => color.gray

This is often clearer than a long if … else if … chain.

once

A compact form for "run this block the first time the condition is true, then never again":

once close > ta.sma(close, 200)
    label.new(bar_index, high, "First close above 200-SMA")

Equivalent to:

var fired = false
if not fired and close > ta.sma(close, 200)
    fired := true
    label.new(bar_index, high, "First close above 200-SMA")

Bare once (no condition) runs its block on the first bar of the chart's history.

Conditional Structures