FCL: what changed
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Title: FCL
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| 1 | + | The *Free Component Library* (**FCL**) consists of a collection of units, providing components (mostly classes) for common tasks. You can also see the [[LCL Components]] available directly within Lazarus. The FCL intends to be compatible with Delphi's *Visual Component Library* (VCL), but the FCL is restricted to non-visual components. On the other hand, the FCL also goes beyond the VCL. | |
| 2 | + | ||
| 3 | + | See [Free Component Library](http://www.freepascal.org/fcl/fcl.var) for the current development status and an overview of the available components (though this seems inconsistent with [Reference for 'fcl'](http://lazarus-ccr.sourceforge.net/docs/fcl/index.html) in Lazarus). You can also check the [source repository](http://www.freepascal.org/cgi-bin/viewcvs.cgi/trunk/packages/). Note that there are also some platform-specific files in the FCL. | |
| 4 | + | ||
| 5 | + | After the example, you can find a list of some FCL components. | |
| 6 | + | ||
| 7 | + | ### Usage | |
| 8 | + | ||
| 9 | + | To use an FCL *component* you need to include the name of the [[Unit|unit]] which implemented it, in a **uses** clause in your program or unit (see example below). The default compiler [[Configuration file|configuration file]] is set up to search the FCL directories for such units. You can also set the appropriate search path with a command-line compiler option of the form -Fu\<path-to-fcl-units\>. | |
| 10 | + | ||
| 11 | + | ### Subpackages | |
| 12 | + | ||
| 13 | + | The full list of subpackages of the FCL can be found here: [[Package List]] | |
| 14 | + | ||
| 15 | + | The fcl-prefixed subpackages are: | |
| 16 | + | ||
| 17 | + | - [[fcl-base]] The base units (including e.g. an [[How To Use TFPExpressionParser|expression parser]]) | |
| 18 | + | - [[fcl-async]] Asynchronous I/O (serial?) | |
| 19 | + | - [[fcl-db]] Generic database support + prepackaged drivers | |
| 20 | + | - [[fcl-fpcunit]] Unit testing framework | |
| 21 | + | - [[fcl-image]] Raster Image reading and writing (aka fpimage) | |
| 22 | + | - [[fcl-json]] Routines for javascript object streaming | |
| 23 | + | - [[fcl-net]] Network related units | |
| 24 | + | - [[fcl-passrc]] Pascal language parsing and transformation | |
| 25 | + | - [[fcl-process]] Process controll | |
| 26 | + | - [[fcl-registry]] Registry | |
| 27 | + | - [[fcl-res]] Resource handling | |
| 28 | + | - [[fcl-stl]] Generic container library (standard template library) | |
| 29 | + | - [[fcl-web]] Helper for web development | |
| 30 | + | - [[fcl-xml]] XML (DOM) unit and related units. | |
| 31 | + | ||
| 32 | + | ### Documentation | |
| 33 | + | ||
| 34 | + | Currently, the FCL is not completely documented (feel free to contribute; also take a look at [[doc:fcl|Reference for 'fcl']]). For Delphi compatible units, you could consult the Delphi documentation. You can always take a look at the source files in the [source repository](http://www.freepascal.org/cgi-bin/viewcvs.cgi/trunk/packages/). | |
| 35 | + | ||
| 36 | + | ### Example | |
| 37 | + | ||
| 38 | + | The following program illustrates the use of the class TObjectList in the FCL unit Contnrs (providing various containers, including lists, stacks, and queues): | |
| 39 | + | ||
| 40 | + | ``` pascal | |
| 41 | + | program TObjectListExample; | |
| 42 | + | {$mode ObjFPC} | |
| 43 | + | uses | |
| 44 | + | Classes, { from RTL for TObject } | |
| 45 | + | Contnrs; { from FCL for TObjectList } | |
| 46 | + | ||
| 47 | + | type | |
| 48 | + | TMyObject = class(TObject) { just some application-specific class } | |
| 49 | + | private | |
| 50 | + | FName: String; { with a string field } | |
| 51 | + | public | |
| 52 | + | constructor Create(AName: String); { and a constructor to create it with a given name } | |
| 53 | + | property Name: String read FName; { and a property to read the name } | |
| 54 | + | end; | |
| 55 | + | ||
| 56 | + | constructor TMyObject.Create(AName: String); | |
| 57 | + | begin | |
| 58 | + | inherited Create; | |
| 59 | + | FName := AName; | |
| 60 | + | end; | |
| 61 | + | ||
| 62 | + | var | |
| 63 | + | VObjectList: TObjectList; { for a list of objects; it is a reference to such a list! } | |
| 64 | + | ||
| 65 | + | begin | |
| 66 | + | VObjectList := TObjectList.Create; { create an empty list } | |
| 67 | + | with VObjectList do | |
| 68 | + | begin | |
| 69 | + | Add(TMyObject.Create('Thing One')); | |
| 70 | + | Writeln((Last as TMyObject).Name); | |
| 71 | + | Add(TMyObject.Create('Thing Two')); | |
| 72 | + | Writeln((Last as TMyObject).Name); | |
| 73 | + | end; | |
| 74 | + | end. | |
| 75 | + | ``` | |
| 76 | + | ||
| 77 | + | This program must be compiled in an object-oriented mode, such as -Mobjfpc or -Mdelphi. | |
| 78 | + | ||
| 79 | + | ### FCL Components | |
| 80 | + | ||
| 81 | + | This is not an exhaustive list (to avoid duplication of effort). It only mentions some important components, or components that are otherwise not easy to find. | |
| 82 | + | ||
| 83 | + | Classes | |
| 84 | + | Base classes for Object Pascal extensions in Delphi mode | |
| 85 | + | ||
| 86 | + | Contnrs | |
| 87 | + | Some common container classes | |
| 88 | + | ||
| 89 | + | [[fpcunit|FPCUnit]] | |
| 90 | + | A Unit testing framework (based on Kent Beck's unit testing framework. See [JUnit](http://www.junit.org/)),[FPCUnit tutorial (pdf)](http://www.freepascal.org/~michael/articles/fpcunit/fpcunit.pdf) | |
| 91 | + | ||
| 92 | + | XMLRead, XMLWrite and DOM | |
| 93 | + | Detailed at the [[XML Tutorial]] | |
| 94 | + | ||
| 95 | + | --- | |
| 96 | + | *From the Free Pascal wiki, page "FCL", as it stood on 2020-02-14 after a change by Trev, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).* |