One of the notable features of Pine Script is the switch
statement, which offers a structured and efficient way to execute different code paths based on variable values. This tutorial will delve into the intricacies of the switch
statement in Pine Script, illustrating its syntax, functionalities, and practical applications.
The switch
statement in Pine Script exists in two forms: one that switches based on different values of a key expression, and another that switches on the evaluation of different expressions. It’s a powerful control structure that directs the flow of execution based on specified conditions.
Syntax of switch
Statement
The general syntax of the switch
statement is as follows:
// With a key expression [[<declaration_mode>] [<type>] <identifier> = ] switch <expression> {<expression> => <local_block>} => <local_block> // Without a key expression [[<declaration_mode>] [<type>] <identifier> = ] switch {<expression> => <local_block>} => <local_block>
The switch
Statement with an Expression
This form uses a key expression to determine which code block to execute. Each case in the switch
structure is defined by an expression followed by =>
and a local block of code.
Example: Moving Average Type Selection
Let’s consider a practical example where we use the switch
statement to select the type of moving average based on user input.
//@version=5 indicator("Switch using an expression", "", true) string maType = input.string("EMA", "MA type", options = ["EMA", "SMA", "RMA", "WMA"]) float ma = switch maType "EMA" => ta.ema(close, 10) "SMA" => ta.sma(close, 10) "RMA" => ta.rma(close,10) "WMA" => ta.wma(close,10) plot(ma)
In this example, maType
is a string variable set by the user. The switch
statement checks maType
and executes the corresponding moving average function. If no match is found, a runtime error is triggered, and float(na)
is returned to maintain type consistency.
The switch
Statement without an Expression
This form of the switch
statement executes blocks based on the evaluation of expressions within the structure.
Example: Strategy Order Selection
Here, we use the switch
statement to determine whether to place a long or short order in a trading strategy.
//@version=5 strategy("Switch without an expression", overlay = true) bool longCondition = ta.crossover( ta.sma(close, 14), ta.sma(close, 28)) bool shortCondition = ta.crossunder(ta.sma(close, 14), ta.sma(close, 28)) switch longCondition => strategy.entry("Long ID", strategy.long) shortCondition => strategy.entry("Short ID", strategy.short)
In this case, longCondition
and shortCondition
are boolean expressions evaluated before the switch
statement. The statement then executes the corresponding strategy entry based on which condition is true.
Key Takeaways
- The
switch
statement in Pine Script offers a structured way to handle multiple conditions. - It can be used with or without a key expression, providing flexibility in scripting.
- Proper understanding and use of the
switch
statement can enhance the efficiency and readability of Pine Script code.
Conclusion
The switch
statement is a versatile tool in Pine Script that simplifies complex conditional structures. By understanding its syntax and practical use cases, traders and scriptwriters can create more efficient and effective scripts for their trading strategies on TradingView.