{"id":7310,"date":"2024-09-04T12:39:55","date_gmt":"2024-09-04T10:39:55","guid":{"rendered":"https:\/\/oopm.org\/?page_id=7310"},"modified":"2025-01-14T13:59:17","modified_gmt":"2025-01-14T12:59:17","slug":"8-1-subclasses","status":"publish","type":"page","link":"https:\/\/oopm.org\/?page_id=7310","title":{"rendered":"8.1 Subclasses"},"content":{"rendered":"
\"image_pdf\"<\/a>\"image_print\"<\/a><\/div>\n

Let us start by looking at a possible description of two different types of accounts, savings accounts and credit accounts. We first show a class representing the notion of savings account. Some of the attributes are the same as in class Account<\/code> from the previous chapters. In addition, new attributes and statements are added: <\/mark><\/p>\n\n\n\n

class<\/strong> SavingsAccount(owner: ref<\/strong> Customer):\n   balance: var<\/strong> float\n   interest: var<\/strong> float\n <\/mark>  releaseDate: var<\/strong> Date\n   <\/mark>addInterest:\n      balance := balance + (balance * interestRate) \/ 100\n   deposit(amount: var<\/strong> float):\n      balance := balance + amount\n   withdraw(amount: var<\/strong> float) -> newB: var<\/strong> float:\n     <\/mark> if (today > releaseDate) :then\n         balance:= balance - amount\n      :else\n         console.print(\"It is not possible to withdraw\")\n      newB := balance\n   newReleaseDate(newDate: var<\/strong> Date, newInterest: var<\/strong> float):\n      releaseDate := newDate\n      interest := newInterest<\/code><\/pre>\n\n\n\n
Compared to class Account<\/code> from the previous chapters, we have added a data-item releaseDate<\/code> of type Date<\/code>. It represents the date to which the customer has agreed to bind his\/her money in order to get a higher interest than on just an ordinary account.<\/p>\n\n\n\n
The method withdraw<\/code> differs from the one in class Account<\/code>, since it is not possible to withdraw money before the release date.<\/p>\n\n\n\n
We have also added a method newReleaseDate<\/code> with parameters newDate<\/code> and newInterest<\/code>. This method may set a new binding period and a new interest rate for a given a given savings account.<\/p>\n\n\n\n
Next let us look at similar description of a class representing the notion of credit account.<\/p>\n\n\n\n
class<\/strong> CreditAccount(owner: ref<\/strong> Customer):\n   balance: var<\/strong> float\n   interest: var<\/strong> float\n   maxCredit: var<\/strong> float\n   addInterest:\n      balance := balance + (balance * interestRate) \/ 100\n   deposit(amount: var<\/strong> float): \n      balance := balance + amount\n   withdraw(amount: var<\/strong> float):\n      if (-balance < maxCredit) :then\n         balance := balance - amount\n      :else \n         console.print(\"Not possible to withdraw beyond max credit\") \n   changeCredit(newMax: var<\/strong> float, newInterest: var<\/strong> float):\n       maxCredit := newCredit\n       interest := newInterest<\/code><\/pre>\n\n\n\n
For a credit account it is possible to overdraw money up to a certain limit defined as the maximum limit. We have added a data-item maxCredit<\/code>, that represents the maximum credit limit of the account.<\/p>\n\n\n\n
We also have a new method changeCredit<\/code>, which can set a new value for the maximum credit and a new interest rate.<\/p>\n\n\n\n
The withdraw<\/code> method is special in the sense that there is a test for not withdrawing beyond the maxLimit<\/code>. We assume tha maxLimit<\/code> is a positive float number. If balance<\/code> is positive the customer has deposited money on the account. If balance<\/code> is negative, the customer has loaned money from the bank.<\/p>\n\n\n\n
As can be seen, the two types of accounts have some attributes in common like owner<\/code>, balance<\/code>, interest<\/code>, addInterest<\/code>, and deposit<\/code>.<\/p>\n\n\n\n
In addition, each of them have attributes that are specific for the kind of account they represent. For class SavingsAccount<\/code> these are releaseDate<\/code> and newBindingPeriod<\/code>. For class SavingsAccount<\/code> these are: maxCredit<\/code> and changeCredit<\/code>.<\/p>\n\n\n\n
In the next section, we show how to define the common attributes of the two classes in a single class that may be used to define these two classes.<\/p>\n\n\n\n
<\/p>\n
\n\t\t<\/a>\n\t\t<\/div>","protected":false},"excerpt":{"rendered":"
Let us start by looking at a possible description of two different types of accounts, savings accounts and credit accounts. We first show a class representing the notion of savings account. Some of the attributes are the same as in class Account from the previous chapters. In addition, new attributes and statements are added: Compared […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":1008,"menu_order":1,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-7310","page","type-page","status-publish","hentry"],"mb":[],"mfb_rest_fields":["title","gutenberg_elementor_mode"],"_links":{"self":[{"href":"https:\/\/oopm.org\/index.php?rest_route=\/wp\/v2\/pages\/7310","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/oopm.org\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/oopm.org\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/oopm.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/oopm.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=7310"}],"version-history":[{"count":10,"href":"https:\/\/oopm.org\/index.php?rest_route=\/wp\/v2\/pages\/7310\/revisions"}],"predecessor-version":[{"id":11125,"href":"https:\/\/oopm.org\/index.php?rest_route=\/wp\/v2\/pages\/7310\/revisions\/11125"}],"up":[{"embeddable":true,"href":"https:\/\/oopm.org\/index.php?rest_route=\/wp\/v2\/pages\/1008"}],"wp:attachment":[{"href":"https:\/\/oopm.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7310"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}