{"id":154,"date":"2023-12-20T15:45:52","date_gmt":"2023-12-20T15:45:52","guid":{"rendered":"https:\/\/xojo.itbib4you.be\/?page_id=154"},"modified":"2023-12-22T15:15:25","modified_gmt":"2023-12-22T15:15:25","slug":"xojo-fundamentals","status":"publish","type":"page","link":"https:\/\/xojo.itbib4you.be\/index.php\/xojo-fundamentals\/","title":{"rendered":"Xojo Fundamentals"},"content":{"rendered":"\n
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Overview<\/a><\/div>\n<\/div>\n\n\n\n

Introduction<\/h2>\n\n\n\n

To introduce the Xojo<\/mark> language, the main features of the language are summarised in this lesson. This lesson should allow the user to add simple code to Event Handlers<\/mark> .<\/p>\n\n\n\n

Variables<\/h2>\n\n\n\n

Xojo is a strongly typed language: variables must be declared before they can be used. The syntax to declare a variable is as follows:<\/p>\n\n\n\n

Var<\/mark> variable name As data type<\/mark><\/pre>\n\n\n\n
Variable names<\/h3>\n\n\n\n
The following rules apply to naming a variable:<\/p>\n\n\n\n
    \n
  • Variable names must always start with a letter;<\/li>\n\n\n\n
  • Variable names may contain letters, numbers and some special characters (for instance underscore (_));<\/li>\n\n\n\n
  • Variable names in Xojo are case-insensitive<\/mark> (FirstName, firstname and FIRSTNAME refer to the same variable).<\/li>\n<\/ul>\n\n\n\n
    Use camel case<\/mark> (first letter is lowercase, subsequent words in the name start with a capital letter) to name variables (for instance firstName)<\/pre>\n\n\n\n
    Data types<\/h3>\n\n\n\n
    The following data types are frequently used:<\/p>\n\n\n\n
    Data type<\/th>Description<\/th>Example<\/th><\/tr><\/thead>
    Integer<\/td>Integer variables contain whole numbers<\/td>Var<\/mark> score As Integer<\/mark>
    score = 15<\/td><\/tr>
    Double<\/td>Double variables contain decimal numbers<\/td>Var<\/mark> salary As Double<\/mark>
    salary = 4567.87<\/td><\/tr>
    Currency<\/td>Fixed-decimal: mainly used for calculations with monetary data<\/td>Var<\/mark> bankBalance As Currency<\/mark>
    bankBalance = 123678.78<\/td><\/tr>
    String<\/td>String variables contain a series of characters<\/td>Var<\/mark> myName As String<\/mark>
    myName = “John”<\/td><\/tr>
    Boolean<\/td>Boolean variables are limited to the values True or False<\/td>Var<\/mark> invoicePaid As Boolean<\/mark>
    invoicePaid = True<\/td><\/tr>
    Color<\/td>Color variables contain color values<\/td>Var<\/mark> highlight As Color<\/mark>
    highlight = Color<\/mark>.Red<\/td><\/tr><\/tbody><\/table>
    Data types<\/figcaption><\/figure>\n\n\n\n
    Mathematical operations<\/h3>\n\n\n\n
    The following operators are used frequently:<\/p>\n\n\n\n
    Operator<\/th>Operation<\/th>Example<\/th><\/tr><\/thead>
    +<\/td>Addition<\/td>5 + 7 = 12<\/td><\/tr>
    –<\/td>Subtraction<\/td>12 – 5 = 7<\/td><\/tr>
    *<\/td>Multiplication<\/td>5 * 3 = 15<\/td><\/tr>
    \/<\/td>Division<\/td>22 \/ 4 = 5.5<\/td><\/tr>
    ^<\/td>Exponentiation<\/td>3 ^ 3 = 27<\/td><\/tr><\/tbody><\/table>
    Mathematical operators<\/figcaption><\/figure>\n\n\n\n
    Complex mathematical expressions are evaluated using the following priority rules (evaluated from left to right):<\/p>\n\n\n\n
      \n
    1. Parenthesis;<\/li>\n\n\n\n
    2. Exponentiation;<\/li>\n\n\n\n
    3. Multiplication and division;<\/li>\n\n\n\n
    4. Addition and subtraction.<\/li>\n<\/ol>\n\n\n\n
      String operations<\/h3>\n\n\n\n
      The +<\/mark> operator can be used to combine (concatenate<\/mark>) strings: <\/p>\n\n\n\n
      Operator<\/th>Operation<\/th>Example<\/th><\/tr><\/thead>
      +<\/td>Concatenation of strings<\/td>“Napoleon ” + “Bonaparte” = “Napoleon Bonaparte”<\/td><\/tr><\/tbody><\/table>
      String operator<\/figcaption><\/figure>\n\n\n\n
      Arrays<\/h2>\n\n\n\n
      An array<\/mark> is a collection of data for a specific data type. An element in an array is accessible through its index<\/mark>. The index<\/mark> of the first element is zero<\/mark> (0<\/mark>). Arrays<\/mark> can be defined as follows:<\/p>\n\n\n\n
      Var<\/mark> arrayName() As dataType<\/mark>\n\nVar<\/mark> arrayName(size1[,size2, size3...]) As dataType<\/mark>\n\nVar<\/mark> arrayName As dataType<\/mark> = Array<\/mark>(value1, value2...)<\/pre>\n\n\n\n
      Examples:<\/mark>\n\nVar<\/mark> months() As String<\/mark>\nmonths.Add(\"January\"<\/mark>)\n\nVar<\/mark> months(12) As String<\/mark>\nmonths(0) = \"January\"<\/mark>\n\nVar<\/mark> months() As String<\/mark> = Array<\/mark>(\"January\"<\/mark>, \"February\"<\/mark>, \"March\"<\/mark>)<\/pre>\n\n\n\n
      The following methods are very useful when editing arrays:<\/p>\n\n\n\n
      Method<\/th>Description<\/th>Example<\/th><\/tr><\/thead>
      Add<\/td>Adds a new element at the end of the array<\/td>months.Add(“January”)<\/td><\/tr>
      AddAt<\/td>Adds a new element at the specified index<\/td>months.AddAt(2,”March”)<\/td><\/tr>
      Count<\/td>Returns the number of elements in an array<\/td>numberElements = months.Count<\/td><\/tr>
      FirstIndex<\/td>Returns index of the first element<\/td>first = months.FirstIndex<\/td><\/tr>
      LastIndex<\/td>Returns index of the last element<\/td>last = months.LastIndex<\/td><\/tr>
      RemoveAll<\/td>Removes all elements<\/td>months.RemoveAll<\/td><\/tr>
      RemoveAt<\/td>Removes the element at the specified index<\/td>months.RemoveAt(2)<\/td><\/tr>
      Sort<\/td>Sorts the array in ascending order<\/td>months.Sort<\/td><\/tr><\/tbody><\/table>
      Array methods<\/figcaption><\/figure>\n\n\n\n
      Assignment statements<\/h2>\n\n\n\n
      The assignment operator in Xojo is =<\/mark>. A variable to the left of the = <\/mark>sign gets a value from the right side of the statement. The value on the right side of the =<\/mark> sign can be a constant, a variable or an expression.<\/p>\n\n\n\n
      variable = constant|variable|expression<\/pre>\n\n\n\n
      Examples:<\/mark>\n\nage = 12\nmyAge = yourAge\ntotalPrice = netPrice + salesTax<\/pre>\n\n\n\n
      Selection statements<\/h2>\n\n\n\n
      A selection statement<\/mark> will select one or more other statements based on the evaluation of a condition<\/mark>. There are two selection statements available in Xojo: If…Then…Else<\/mark> and Select…Case<\/mark>.<\/p>\n\n\n\n
      A conditional expression evaluates whether a relation between two values is True<\/mark> or False<\/mark>. In most cases, relational operators<\/mark> will be used to define a condition. Xojo defines the following relational operators:<\/p>\n\n\n\n
      Operator<\/th>Definition<\/th><\/tr><\/thead>
      =<\/td>Equal<\/td><\/tr>
      ><\/td>Greater than<\/td><\/tr>
      >=<\/td>Greater than or equal to<\/td><\/tr>
      <<\/td>Less than<\/td><\/tr>
      <=<\/td>Less than or equal to<\/td><\/tr>
      <><\/td>Not equal<\/td><\/tr><\/tbody><\/table>
      Relational operators<\/figcaption><\/figure>\n\n\n\n
      Logical operators<\/mark> can be used to combine two conditional expressions into one logical expression:<\/p>\n\n\n\n
      Operator<\/th>Definition<\/th><\/tr><\/thead>
      And<\/td>AND (True<\/mark> if both<\/mark> conditions are True<\/mark>)<\/td><\/tr>
      Or<\/td>OR (True<\/mark> if any<\/mark> condition is True<\/mark>)<\/td><\/tr>
      Not<\/td>Not (inverts the result of a logical expression – If expression evaluates to True<\/mark>, Not<\/mark> returns False<\/mark>. If expression evaluates to False<\/mark>, Not<\/mark> returns True<\/mark>.)<\/td><\/tr><\/tbody><\/table>
      Logical operators<\/figcaption><\/figure>\n\n\n\n
      If…Then…Else<\/h3>\n\n\n\n
      The If…Then…Else<\/mark> statement has the following syntax:<\/p>\n\n\n\n
      If<\/mark> conditional expression1 Then<\/mark>\n   statement(s)\nElseIf<\/mark> conditional expression2 Then<\/mark>\n   statements(s)\nElseIf<\/mark> conditional expression3 Then<\/mark>\n   ...\nElse<\/mark>\n   statement(s)\nEnd If<\/mark><\/pre>\n\n\n\n
      ElseIf <\/mark>and Else<\/mark> statements are optional. If the first conditional expression is True <\/mark>then the statements following the Then<\/mark> keyword are executed. If the first conditional expression is False<\/mark> then the ElseIf<\/mark> condition (if present) will be evaluated. If none<\/mark> of the conditional expressions are True<\/mark> then the Else <\/mark>statements (if present) will be executed.<\/p>\n\n\n\n
      Example:<\/mark>\n\nVar<\/mark> discountCode As Integer<\/mark>\nVar<\/mark> discount As Integer<\/mark>\n\nIf<\/mark> discountCode = 1 Then<\/mark>\n   discount = 5\nElseIf<\/mark> discountCode = 2\n   discount = 10\nElse<\/mark>\n   discount = 0\nEnd If<\/mark><\/pre>\n\n\n\n
      Select…Case<\/h3>\n\n\n\n
      The Select…Case<\/mark> statement tests a variable for a possible value. When the variable matches one of the values \u200b\u200blisted in a Case<\/mark>, the code following that Case<\/mark> keyword is executed. The Else<\/mark> sentence (no match was found) is optional.<\/p>\n\n\n\n
      The Select…Case<\/mark> statement has the following syntax:<\/p>\n\n\n\n
      Select Case<\/mark> variable\nCase<\/mark> value1\n   statement(s)\nCase<\/mark> value2\n   statement(s)\nCase<\/mark> value3\n   ...\nElse<\/mark>\n   statement(s)\nEnd Select<\/mark><\/pre>\n\n\n\n
      Example:<\/mark>\n\nVar<\/mark> discountCode As Integer<\/mark>\nVar<\/mark> discount As Integer<\/mark>\n\nSelect Case<\/mark> discountCode\nCase<\/mark> 1\n   discount = 5\nCase<\/mark> 2\n   discount = 10\nElse<\/mark>\n   discount = 0\nEnd Select<\/mark><\/pre>\n\n\n\n
      Iteration statements<\/h2>\n\n\n\n
      Xojo has three statements to execute one or more lines of code multiple times: For…Next<\/mark>, While…Wend<\/mark>, Do…Loop<\/mark>.<\/p>\n\n\n\n
      For…Next<\/h3>\n\n\n\n
      A For…Next <\/mark>statement is useful when you know how many times the iteration must run. The For…Next<\/mark> has the following syntax:<\/p>\n\n\n\n
      For<\/mark> variable = startValue To<\/mark> endValue Step<\/mark> stepValue\n   statement(s)\nNext<\/mark><\/pre>\n\n\n\n
      The Step<\/mark> clause is optional. startValue<\/mark>, endValue<\/mark> and stepValue<\/mark> can be a constant or a variable.<\/p>\n\n\n\n
      Example:<\/mark>\n\nVar<\/mark> counterAs Integer<\/mark>\nVar <\/mark>sum As Integer<\/mark> = 0\n\nFor<\/mark> counter = 1 To<\/mark> 10 Step<\/mark> 1\n   sum = sum + counter\nNext<\/mark><\/pre>\n\n\n\n
      While…Wend<\/h3>\n\n\n\n
      A While…Wend<\/mark> statement will run the lines of code between the While<\/mark> and the Wend<\/mark> sentences as long as<\/mark> the conditional expression evaluates to True<\/mark>. If the condition evaluates to False<\/mark> the execution will continue with the code after the Wend<\/mark> sentence. If the condition is already False<\/mark> at the start of the iteration then the iteration instructions will not be executed. The While…Wend<\/mark> statement has the following syntax:<\/p>\n\n\n\n
      While<\/mark> conditional expression \n   statement(s)\nWend<\/mark><\/pre>\n\n\n\n
      Example:<\/mark>\n\nVar<\/mark> counterAs Integer<\/mark> = 1\nVar <\/mark>sum As Integer<\/mark> = 0\n\nWhile<\/mark> counter <= 10\n   sum = sum + counter\n   counter = counter + 1\nWend<\/mark><\/pre>\n\n\n\n
      Do…Loop<\/h3>\n\n\n\n
      The Do…Loop<\/mark> statement will execute all lines of code between the Do<\/mark> and the Loop<\/mark> keywords until<\/mark> the condition evaluates to True<\/mark>. The conditional expression can either be at the beginning or at the end of the Do…Loop<\/mark>. The Do…Loop<\/mark> statement has the following syntax:<\/p>\n\n\n\n
      Do Until<\/mark> conditional expression\n   statement(s)\nLoop<\/mark>\n\nOr<\/mark>\n\nDo<\/mark>\n   statement(s)\nLoop Until<\/mark> conditional expression<\/pre>\n\n\n\n
      Example:<\/mark>\n\nVar<\/mark> counterAs Integer<\/mark> = 1\nVar <\/mark>sum As Integer<\/mark> = 0\n\nDo Until<\/mark> counter > 10\n   sum = sum + counter\n   counter = counter + 1\nLoop<\/mark><\/pre>\n","protected":false},"excerpt":{"rendered":"
      Introduction To introduce the Xojo language, the main features of the language are summarised in this lesson. This lesson should allow the user to add simple code to Event Handlers . Variables Xojo is a strongly typed language: variables must be declared before they can be used. The syntax to declare a variable is as … Continue reading “Xojo Fundamentals”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-154","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/pages\/154","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/comments?post=154"}],"version-history":[{"count":57,"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/pages\/154\/revisions"}],"predecessor-version":[{"id":223,"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/pages\/154\/revisions\/223"}],"wp:attachment":[{"href":"https:\/\/xojo.itbib4you.be\/index.php\/wp-json\/wp\/v2\/media?parent=154"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}