The if then else instruction is used to determine which instruction or set of instructions will be executed, depending on one or more conditions.
A condition is specified trough an expression of type yes_no.
The if then else instruction can be used in different ways, as shown in the following table:
Table 8.8. if then else variations
if then | One set of instructions is executed if one condition is fulfilled. |
if then else | One set of instructions is executed if one condition is fulfilled and another set of instructions is executed if the same condition is not fulfilled. |
if then elseif else | Several conditions are specified, and the first condition that is fulfilled determines which set of instructions is executed. If no condition is fulfilled then the optional else clause can be used to specify another set of instructions that will be executed in that case. |
![[Note]](images/note.png) | Note |
|---|---|
The if then else instruction in Obix is very similar to the if then else statement in Java, C#, and other programming languages. It is a fundamental flow control instruction (statement) that allows executing instructions conditionally. |
Table 8.9. if then else syntax
| Production | Syntax | Links |
|---|---|---|
if_then_else_instruction |
| the section called “if then else instruction” |
Example 8.6. if then else examples
service instruction_examples
command if_then_else_examples
script
// ask user to enter a, b or c on the system console
const string user_input = se_console.co_ask_string ( "Please enter a, b or c: " )
// 'if then' variation (simplest form)
if user_input =v "a" then
se_console.co_message ( "You typed a." )
end if
// 'if then else' variation
if user_input =v "a" then
console.message ( "You typed a." )
else
console.message ( "You didn't type a." )
// nested if
if user_input =v "A" then
console.message ( "But you typed A." )
end if
end if
// 'if then elseif else' variation
if user_input =v "a" then
console.message ( "You typed a." )
else if user_input =v "b" then
console.message ( "You typed b." )
else if user_input =v "c" then
console.message ( "You typed c." )
else
console.message ( "You didn't type a, b or c." )
console.message ( "Shame on you!" )
end if
// alternative to achieve the same result:
if user_input =v "a" or user_input =v "b" or user_input =v "c" then
console.message ( "You typed " & user_input & "." )
else
console.message ( "You didn't type a, b or c." )
console.message ( "Shame on you!" )
end if
end script
end command
end service