{"id":258,"date":"2024-02-20T14:36:58","date_gmt":"2024-02-20T14:36:58","guid":{"rendered":"https:\/\/xojo.itbib4you.be\/?page_id=258"},"modified":"2024-11-27T07:26:27","modified_gmt":"2024-11-27T07:26:27","slug":"the-account-class","status":"publish","type":"page","link":"https:\/\/xojo.itbib4you.be\/index.php\/the-account-class\/","title":{"rendered":"The Account Class"},"content":{"rendered":"\n
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Overview<\/a><\/div>\n<\/div>\n\n\n\n

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

In this lesson we will define the Account <\/mark>class as discussed in the previous lesson. Member data (properties<\/mark>) will be added to the class and member methods<\/mark> are developed and inserted into the class.<\/p>\n\n\n\n

How define a new Class?<\/h2>\n\n\n
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\"\"<\/figure>\n<\/div>\n\n\n

A new class can be inserted in a program by selecting Class<\/mark> from the Insert<\/mark> button on the toolbar (see red<\/mark> arrow on screenshot) or from the Insert<\/mark> menu item.<\/p>\n\n\n\n

<\/div>\n\n\n
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\"\"<\/figure>\n<\/div>\n\n\n

In the Inspector<\/mark> we change the default name of the class (Class1<\/mark>) into Account<\/mark>.<\/p>\n\n\n\n

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Add a property to a Class<\/h2>\n\n\n
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\"Insert<\/figure>\n<\/div>\n\n\n

To add a property to the class, you must first select the class in the Navigator<\/mark>. The small +<\/mark> button above the coding pane (see blue<\/mark> arrow on the screenshot) allows you to add various code items (Menu Handler, Method, Note, Property…). Select Property<\/mark> (see red<\/mark> arrow on the screenshot).<\/p>\n\n\n\n

<\/div>\n\n\n
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\"\"<\/figure>\n<\/div>\n\n\n

In the Inspector<\/mark> we can change the characteristics of the new property: the default Name<\/mark> (default Untitled<\/mark>) into AccountBalance<\/mark> , the default data Type<\/mark> (default Integer<\/mark>) into Currency<\/mark> and we limit the Scope<\/mark> of the property to Private<\/mark>.<\/p>\n\n\n\n

It is good practice to set properties and methods to Private<\/mark> if they are not needed outside the class.<\/pre>\n\n\n\n
Add a method to a Class<\/h2>\n\n\n
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\"\"<\/figure>\n<\/div>\n\n\n
To add a method to a class, you must first select the class in the Navigator<\/mark>. The small +<\/mark> button above the coding pane (see blue<\/mark> arrow on the screenshot) allows you to add various code items (Menu Handler, Method, Note, Property…). Select Method<\/mark> (see red<\/mark> arrow on the screenshot).<\/p>\n\n\n\n
DepositMoney<\/h3>\n\n\n
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\"\"<\/figure>\n<\/div>\n\n\n
Now, the Method Name<\/mark>, the Parameters<\/mark>, the Return Type<\/mark> and the Scope<\/mark> of the new method can be defined in the Inspector<\/mark> (see screenshot).<\/p>\n\n\n\n
<\/div>\n\n\n\n
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  • Method Name<\/mark>: the name of the method. This name must be used in the code to call the method;<\/li>\n\n\n\n
  • Parameters<\/mark>: the name<\/mark> and data type<\/mark> of variables that will receive data passed from the  calling code. Parameters are separated by commas. These variables will be used in the new method (for instance amount As Currency<\/mark> : amount is a variable (parameter) that can be used in the method);<\/li>\n\n\n\n
  • Return Type<\/mark>: some methods will return a value to the line of code that called the method. The Return Type<\/mark> specifies the data type of the returned value;<\/li>\n\n\n\n
  • Scope<\/mark>: indicates the accessibility (public, private, protected) of the method in the application.<\/li>\n<\/ul>\n\n\n\n
    The method code can be entered in the blank code editor. Our code is simple: increase the property AccountBalance<\/mark> with the deposited value available in the parameter amount<\/mark>.<\/p>\n\n\n\n
    AccountBalance = AccountBalance + amount<\/pre>\n\n\n\n
    WithdrawMoney<\/h3>\n\n\n
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    \"\"<\/figure>\n<\/div>\n\n\n
    The definition of the method WithdrawMoney<\/mark> is similar to the previous definition.<\/p>\n\n\n\n
    <\/div>\n\n\n\n
    However, no more money can be withdrawn than the balance of the account. The following code has been entered in the code editor:<\/p>\n\n\n\n
    \/\/the value of amount cannot be greater than the value of AccountBalance<\/mark>\nIf amount > AccountBalance Then\n  amount = AccountBalance\nEnd If\nAccountBalance = AccountBalance - amount<\/pre>\n\n\n\n
    \/\/<\/mark> Is used to add comments to the code<\/pre>\n\n\n\n
    GetBalance<\/h3>\n\n\n
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    \"\"<\/figure>\n<\/div>\n\n\n
    Since the property AccountBalance<\/mark> is a private property, we need a public method (GetBalance<\/mark>) to access this private property. The method GetBalance<\/mark> will return the value of AccountBalance<\/mark> (data type Currency<\/mark>) to the calling line of code.<\/p>\n\n\n\n
    <\/div>\n\n\n\n
    The code in the code editor is limited to one line:<\/p>\n\n\n\n
    Return<\/mark> AccountBalance<\/pre>\n\n\n\n
    The AccountWindow<\/h2>\n\n\n
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    \"AccountWindow\"<\/figure>\n<\/div>\n\n\n
    The window named AccountWindow<\/mark> contains 3 buttons and one label:<\/p>\n\n\n\n