The ShortString type corresponds to the typical Pascal strings, as described before.

To overcome the limits of traditional Pascal strings, the 32-bit versions of Delphi support long strings. This is demonstrated by the fact that you can access a specific string character using the notation. In fact, a string is almost an array of characters. Each string is defined with a fixed size (which by default is the maximum, 255), although you can declare shorter strings to save memory space.Ī string type is similar to an array type. Because the length is expressed by a single byte, it cannot exceed 255 characters, a very low value that creates many problems for string manipulation. In Borland's Turbo Pascal and in 16-bit Delphi, the typical string type is a sequence of characters with a length byte at the beginning, indicating the current size of the string. Pascal has a traditional way of handling strings, Windows has its own way, borrowed from the C language, and 32-bit versions of Delphi include a powerful long string data type, which is the default string type in Delphi.

String handling in Delphi is quite simple, but behind the scenes the situation is quite complex.

The cover of the 4th edition of Essential Pascal, Perhaps is better to go on this path rather than to reinvent the wheel.Essential Pascal on Marco Web Center And, of course, you have the OnValidate event where you can do a test if 'Age' is between 0 and 33 (for example). for the 'Age' field the input is restricted to numbers only.

Editing - you have dedicated controls for each data type (including grids for multi-row input).

Of course you can clear the filter, reversing the action: Setting the Filter property to 'False' - or - issuing an SQL like: 'SELECT * FROM PETS' (without the WHERE clause) etc. Also you can use OnFilterRecord event for that. In the case of RDBMSes you can achieve it in the same way and/or using a standard SQL: 'SELECT * FROM PETS WHERE BREED='foo' ORDER BY NAME. In the case of memory datasets setting the Filter property to Breed='foo' and the Filtered property to 'True' is enough.

Filter - you can do any reversible filtering on any field with any operator you like.

Sort - There are simple methods to do this or if you'll choose a SQL backend a simple 'SELECT * FROM PETS ORDER BY NAME' will do your job.

In the case of memory datasets you have methods like Load/SaveToFile

Persistence (storage) - your RDBMS will take care of that.

In this way you have solved the following problems:

(You can use memory datasets like TClientDataSet, JVCL's TjvMemoryData or any other TDataSet descendant including full-blown RDBMS) You can store your objects in a data set.

Delphi 7 listbox selected item