Keyword # ByRef --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ## Description Used to pass a parameter by reference. ## Usage ``` xojo ByRef parameter As DataType ``` | Part | Type | Description | |-----------|---------------------|-------------------------------------------------------------------| | parameter | | Parameter to be passed by reference. *parameter* can be an array. | | DataType | Any valid data type | The data type of the parameter. | ## Notes Parameters passed by value are treated as local variables inside the method-just like variables that are created using the `Var` statement. This means that you can modify the values of the parameters themselves rather than first assigning the parameter to a local variable. For example, if you pass a value in the parameter "x", you can increment or decrement the value of x rather then assigning the value of x to a local variable that is created using `Var`. To pass a parameter by reference, you use the ByRef keyword in the parameter declaration for the method. If you precede a parameter name by the keyword ByRef, you pass information by reference. When you pass information by reference, you actually pass a pointer to the variable containing the information. The practical advantage of this technique is that the method can change the values of each parameter. When you pass parameters by value, it doesn't do this because in effect the parameter only represents a copy of the data itself.
Note
Passing array parameters with ByRef is not currently supported for Android.
## Sample code The following method declaration uses \`ByRef\`: ``` xojo ByRef amount As Double ``` --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- When you click OK to save the new method, the Sub statement in the Code Editor shows that the parameter has been declared \`ByRef\`: ``` xojo Protected Sub AddTax(ByRef amount As Double) ``` --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- The AddTax method takes one parameter, amount, that is called ByRef. The method code is: ``` xojo amount = amount * 1.08 ``` --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- AddTax is called in the following code: ``` xojo Var a As Double a = 3 AddTax(a) TextField1.Text = a.ToString ``` ## Compatibility | | | |-----------------------|-----| | **Project Types** | All | | **Operating Systems** | All |
`ByVal` keyword.