Keyword # Static --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- ## Description Creates a local variable or local array with the name and size (in the case of an array) and data type specified. A variable declared with the Static statement and assigned a value retains its value from one invocation of the method to the next. In contrast, variables declared with the `Var` statement are completely local to the method and are destroyed when each invocation of the method goes out of scope. ## Usage The Static statement has two syntaxes: ``` xojo Static variableName [ , variableNameN ] As [ New ] DataType [ = InitialValue ] ``` | Part | Type | Description | |---------------|-------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------| | variableName | Variable name | The name of the new variable. | | variableNameN | Variable name | Optional. The names of other variables you wish to create with the same data type. | | DataType | Data type name | The data type of the variable. | | InitialValue | Same type as *DataType* | Initial value for *variableName*. If the datatype is an object that requires instantiation via the `New` operator, you can do that instead of assigning an initial value. | **or** ``` xojo Static arrayName(size [ , sizeN ]) As DataType ``` | Part | Type | Description | |-----------|------------------------------------|------------------------------------------------------------------------------------------------------| | arrayName | Variable name | The name of the new array. | | size | `Integer` | The size (number of elements) for the array. Arrays are zero-based. | | sizeN | `Integer` | Optional. The size of the next dimension of the array if you are creating a multi-dimensional array. | | DataType | Data type name | The data type of the array. | ## Notes A Static variable is equivalent to a local variable declared by the `Var` statement but its value is retained between several calls of the method it is declared in. Also, all the instances of a given class share the same Static values.
Note
Whenever you assign an initial value to a Static variable using the equal sign, the assignment will occur only once when the method is called for the very first time.
For example, if you want a serial number to be generated, i.e. a method with always returns a new increasing value, the simplest is to use a Static value as: ``` xojo Function SerialNumber() As Integer Static currentSerialNumber As Integer = 0 currentSerialNumber = currentSerialNumber + 1 ' Increment the value Return currentSerialNumber ' Return the value End Function ``` You can also use Static to cache a value which takes time to get so you can improve the performance of your code: ``` xojo Computed Property MyCachedProperty Get ' Inside the Get part Static theProperty As String = AMethodWhichTakesSomeTime ' This will be executed only the first time Return theProperty End Get ``` ## Sample code This example uses the Static statement to create an `Integer` variable called "age" and assigns it the value 33. ``` xojo Static age As Integer = 33 ``` --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- This example uses the Static statement to create two `string` variables. ``` xojo Static FirstName, LastName As String ``` --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- This example uses the Static statement to create an array called aNames with 11 elements (remember, arrays have a zero element). ``` xojo Static aNames(10) As String ``` --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- This example uses the Static statement to create an array called aNames with one element. ``` xojo Static aNames(0) As String ``` ## Compatibility | | | |-----------------------|-----| | **Project Types** | All | | **Operating Systems** | All |
`Arrays` concept; `Collection`, `Dictionary` classes; `Var` statement.