Swift Function – Pass Parameter by Reference
To pass parameter by reference to a Swift function, define this parameter with inout
keyword, and use preface the parameter in function call with ampersand (&).
The syntax to pass parameter by reference to a function in Swift is
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func functionName(parameterName: inout Type) {
//body
}
var param: Type = initialValue
functionName(¶m)
Example
In the following program, we define a function incrementByN()
where the parameter x
is defined as inout
. When we call this function, we pass the variable someNumber
by reference using ampersand.
main.swift
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func incrementByN(x: inout Int, n: Int = 0) {
x = x + n
}
var someNumber = 10
print("someNumber before function call : \(someNumber)")
incrementByN(x: &someNumber, n: 7)
print("someNumber after function call : \(someNumber)")
Output
Conclusion
In this Swift Tutorial, we learned how to pass parameter by reference to a function.