A 4D component is a set of 4D functions, methods, and forms representing one or more functionalities that can be installed and used in 4D applications. For example, you can develop a 4D e-mail component that manages every aspect of sending, receiving and storing e-mails in 4D applications.
You can develop 4D components for your own needs and keep them private. You can also share your components with the 4D community.
- Matrix Project: 4D project used for developing the component. The matrix project is a standard project with no specific attributes. A matrix project forms a single component.
- Host Project: Application project in which a component is installed and used.
- Component: Matrix project that can be compiled or built, copied into the
Componentsfolder of the host application and whose contents are used in the host application.
Creating and installing 4D components is carried out directly from 4D:
- To install a component, you simply need to copy the component files into the
Componentsfolder of the project. You can use aliases or shortcuts.
- A project can be both a matrix and a host, in other words, a matrix project can itself use one or more components. However, a component cannot use "sub-components" itself.
- A component can call on most of the 4D elements: classes, functions, project methods, project forms, menu bars, choice lists, and so on. Não pode chamar métodos de bancos de dados e triggers.
- You cannot use the datastore, standard tables, or data files in 4D components. Entretanto um componente não pode criar ou usar tabelas, campos e arquivos de dados usando mecanismos de bancos de dados externos. São bancos 4D independentes com as que se trabalha utilizando comandos SQL.
- A host project running in interpreted mode can use either interpreted or compiled components. A host project running in compiled mode cannot use interpreted components. In this case, only compiled components can be used.
Escopo dos comandos de linguagem
Exceto pelos Comandos não utilizáveis, um componente não pode usar qualquer comando da linguagem 4D.
When commands are called from a component, they are executed in the context of the component, except for the
EXECUTE METHOD or
EXECUTE FORMULA command that use the context of the method specified by the command. Also note that the read commands of the “Users and Groups” theme can be used from a component but will read the users and groups of the host project (a component does not have its own users and groups).
SET DATABASE PARAMETER and
Get database parameter commands are an exception: their scope is global to the application. When these commands are called from a component, they are applied to the host application project.
Além disso, medidas especificas foram criadas para os comandos
Structure file e
Get 4D folder quando utilizados no marco dos componentes.
COMPONENT LIST command can be used to obtain the list of components that are loaded by the host project.
Comandos não utilizáveis
Os comandos abaixo nãoo são compatíveis para seu uso dentro de um componente porque modificam o arquivo de estrutura - que está aberto em apenas leitura. Their execution in a component will generate the error -10511, "The CommandName command cannot be called from a component":
ON EVENT CALL
Method called on event
SET PICTURE TO LIBRARY
REMOVE PICTURE FROM LIBRARY
ARRAY TO LIST
CREATE USER FORM
DELETE USER FORM
Set group properties
Set user properties
BLOB TO USERS
SET PLUGIN ACCESS
- O comando
Current form tabledevolve
Nilquando chamado no contexto de um formulário projeto. Por isso não pode ser usado em um componente.
- SQL data definition language commands (
DROP TABLE, etc.) cannot be used on the component project. Entretanto são compatíveis com bancos de dados externos (ver o comando SQL
Partilhar os métodos de projeto
All the project methods of a matrix project are by definition included in the component (the project is the component), which means that they can be called and executed within the component.
On the other hand, by default these project methods will not be visible, and they can't be called in the host project. In the matrix project, you must explicitly designate the methods that you want to share with the host project by checking the Shared by components and host project box in the method properties dialog box:
Shared project methods can be called in the code of the host project (but they cannot be modified in the Code Editor of the host project). These methods are entry points of the component.
Conversely, for security reasons, by default a component cannot execute project methods belonging to the host project. In certain cases, you may need to allow a component to access the project methods of your host project. To do this, you must explicitly designate which project methods of the host project you want to make accessible to the components (in the method properties, check the Shared by components and host project box).
Once the project methods of the host projects are available to the components, you can execute a host method from inside a component using the
EXECUTE FORMULA or
EXECUTE METHOD commands. Por exemplo:
// Host Method component_method("host_method_name")
// component_method C_TEXT($1) EXECUTE METHOD($1)
An interpreted host database that contains interpreted components can be compiled or syntax checked if it does not call methods of the interpreted component. Otherwise, a warning dialog box appears when you attempt to launch the compilation or a syntax check and it will not be possible to carry out the operation.
Keep in mind that an interpreted method can call a compiled method, but not the reverse, except via the use of the
Sharing of classes and functions
By default, component classes and functions cannot be called from the 4D Code Editor of the host project. If you want your component classes and functions to be exposed in the host projects, you need to declare a component namespace. Additionally, you can control how component classes and functions are suggested in the host Code Editor.
Declaring the component namespace
To allow classes and functions of your component to be exposed in the host projects, enter a value in the Component namespace in the class store option in the General page of the matrix project Settings. By default, the area is empty: component classes are not available outside of the component context.
A namespace ensures that no conflict emerges when a host project uses different components that have classes or functions with identical names. A component namespace must be compliant with property naming rules.
When you enter a value, you declare that component classes and functions will be available in the user class store (cs) of the host project's code, through the
cs.<value> namespace. For example, if you enter "eGeometry" as component namespace, assuming that you have created a
Rectangle class containing a
getArea() function, once your project is installed as a component, the developer of the host project can write:
//in host project var $rect: cs.eGeometry. Rectangle $rect:=cs.eGeometry. Rectangle.new(10;20) $area:=$rect.getArea()
Of course, it is recommended to use a distinguished name to avoid any conflict. If a user class with the same name as a component already exists in the project, the user class is taken into account and the component classes are ignored.
A component's ORDA classes are not available in its host project. For example, if there is a dataclass called Employees in your component, you will not be able to use a "cs. Mycomponent. Employee" class in the host project.
Just like in any project, you can create hidden classes and functions in the component by prefixing names with an underscore ("_"). When a component namespace is defined, hidden classes and functions of the component will not appear as suggestions when using code completion.
Note however that they can still be used if you know their names. For example, the following syntax is valid even if the
_Rectangle class is hidden:
Non-hidden functions inside a hidden class appear as suggestions when you use code completion with a class that inherits from it. For example, if a component has a
Teacherclass that inherits from a
_Personclass, code completion for
Teachersuggests non-hidden functions from
Code completion for compiled components
To make your component easier to use for developers, you can check the Generate syntax file for code completion when compiled option in the General page of the matrix project Settings.
A syntax file (JSON format) is then automatically created during the compilation phase, filled with the syntax of your component's classes, functions, and exposed methods, and placed in the \Resources\en.lproj folder of the component project. 4D uses the contents of that syntax file to generate contextual help in the code editor, such as code completion and function syntax:
If you don't enter a component namespace, the resources for the classes and exposed methods are not generated even if the syntax file option is checked.
The local, process and interprocess variables are not shared between components and host projects. The only way to modify component variables from the host project and vice versa is using pointers.
Exemplo usando um array:
//In the host project: ARRAY INTEGER(MyArray;10) AMethod(->MyArray) //In the component, the AMethod project method contains: APPEND TO ARRAY($1->;2)
Exemplos usando variáveis:
Without a pointer, a component can still access the value of a host database variable (but not the variable itself) and vice versa:
//In the host database C_TEXT($input_t) $input_t:="DoSomething" component_method($input_t) // component_method gets "DoSomething" in $1 (but not the $input_t variable)
When you use pointers to allow components and the host project to communicate, you need to take the following specificities into account:
Get pointercommand will not return a pointer to a variable of the host project if it is called from a component and vice versa.
The component architecture allows the coexistence, within the same interpreted project, of both interpreted and compiled components (conversely, only compiled components can be used in a compiled project). Para utilizar apontadores neste caso, deve respeitar o seguinte princípio: o intérprete pode desconectar um ponteiro construído em modo compilado; no entanto, em modo compilado, não pode deconectar um ponteiro construído em modo interpretado. In order to use pointers in this case, you must respect the following principle: the interpreter can unpoint a pointer built in compiled mode; however, in compiled mode, you cannot unpoint a pointer built in interpreted mode.
Se o componente C definir a variável
myCvar, o componente I pode acessar ao valor desta variável utilizando o ponteiro
Se o componente I definir a variável
myIvar, o componente C não pode acessar essa variável usando o ponteiro
->myIvar. Esta sintaxe causa um erro de execução.
The comparison of pointers using the
RESOLVE POINTERcommand is not recommended with components since the principle of partitioning variables allows the coexistence of variables having the same name but with radically different contents in a component and the host project (or another component). O tipo da variável pode mesmo ser diferente em ambos os contextos. Se o
myptr2apontar cada ponto para uma variável, a comparação seguinte produzirá um resultado incorrecto:
RESOLVE POINTER(myptr1;vVarName1;vtablenum1;vfieldnum1) RESOLVE POINTER(myptr2;vVarName2;vtablenum2;vfieldnum2) If(vVarName1=vVarName2) //Este teste retorna True mesmo se as variáveis forem diferentes
Neste caso é preciso usar a comparação de ponteiros:
If(myptr1=myptr2) //Este teste retorna False
Gestão de erros
An error-handling method installed by the
ON ERR CALL command only applies to the running application. In the case of an error generated by a component, the
ON ERR CALL error-handling method of the host project is not called, and vice versa.
Access to tables of the host project
Although components cannot use tables, pointers can allow host projects and components to communicate with each other. Por exemplo, aqui está um método que pode ser chamado a partir de um componente:
// chamar a um método componente methCreateRec(->[PEOPLE];->[PEOPLE]Name;"Julie Andrews")
Dentro do componente, o código do método
C_POINTER($1) //Pointer on a table in host project C_POINTER($2) //Pointer on a field in host project C_TEXT($3) // Value to insert $tablepointer:=$1 $fieldpointer:=$2 CREATE RECORD($tablepointer->) $fieldpointer->:=$3 SAVE RECORD($tablepointer->)
In the context of a component, 4D assumes that a reference to a table form is a reference to the host table form (as components can't have tables.)
Uso de tabelas e campos
A component cannot use the tables and fields defined in the 4D structure of the matrix project. Mas pode criar e usar bancos de dados externos e então usar suas tabelas e campos de acordo com suas necessidades. Pode criar e gerenciar bancos de dados externos usando SQL. Mas pode criar e usar bancos de dados externos e então usar suas tabelas e campos de acordo com suas necessidades. Usar um banco externo significa designar temporariamente esse banco de dados como o banco atual, em outras palavras, o banco alvo para as pesquisas SQL executadas por 4D. Pode criar bancos externos usando o comando SQL
O código abaixo está incluído em um componente e realiza três ações básicas com um banco externo:
- cria o banco externo se não existir ainda
- adiciona dados ao banco externo,
- lê dados do banco externo.
Cria o banco externo:
<>MyDatabase:=Get 4D folder+"\MyDB" // (Windows) armazena os dados em um diretório autorizado Begin SQL CREATE DATABASE IF NOT EXISTS DATAFILE :[<>MyDatabase]; USE DATABASE DATAFILE :[<>MyDatabase]; CREATE TABLE IF NOT EXISTS KEEPIT ( ID INT32 PRIMARY KEY, kind VARCHAR, name VARCHAR, code TEXT, sort_order INT32 ); CREATE UNIQUE INDEX id_index ON KEEPIT (ID); USE DATABASE SQL_INTERNAL; End SQL
Escrita no banco de dados externa:
$Ptr_1:=$2 // retrieves data from the host project through pointers $Ptr_2:=$3 $Ptr_3:=$4 $Ptr_4:=$5 $Ptr_5:=$6 Begin SQL USE DATABASE DATAFILE :[<>MyDatabase]; INSERT INTO KEEPIT (ID, kind, name, code, sort_order) VALUES (:[$Ptr_1], :[$Ptr_2], :[$Ptr_3], :[$Ptr_4], :[$Ptr_5]); USE DATABASE SQL_INTERNAL; End SQL
Lendo de um banco externo:
$Ptr_1:=$2 // accesses data of the host project through pointers $Ptr_2:=$3 $Ptr_3:=$4 $Ptr_4:=$5 $Ptr_5:=$6 Begin SQL USE DATABASE DATAFILE :[<>MyDatabase]; SELECT ALL ID, kind, name, code, sort_order FROM KEEPIT INTO :$Ptr_1, :$Ptr_2, :$Ptr_3, :$Ptr_4, :$Ptr_5; USE DATABASE SQL_INTERNAL; End SQL
Uso de formulários
- Só os "formulários de projeto" (formulários que não estejam associados a nenhuma tabela específica) podem ser utilizados em um componente. Só os "formulários de projeto" (formulários que não estejam associados a nenhuma tabela específica) podem ser utilizados em um componente.
- A component can call table forms of the host project. Note que nesse caso é necessário usar ponteiros ao invés de nomes de tabelas entre colchetes  para especificar os formulários no código do componente.
If a component uses the
ADD RECORDcommand, the current Input form of the host project will be displayed, in the context of the host project. Consequently, if the form includes variables, the component will not have access to them.
- You can publish component forms as subforms in the host projects. Pode publicar formulários componentes como subformulários no banco de dados local Isso significa que pode desenvolver componentes oferecendo objetos gráficos. Por exemplo, Widgets fornecidos por 4D são baseados no uso de subformulários em componentes.
In the context of a component, any referenced project form must belong to the component. For example, inside a component, referencing a host project form using
Open form windowwill throw an error.
Uso de recursos
Components can use resources located in the Resources folder of the component.
Mecanismos automáticos são operacionais: os arquivos XLIFF encontrados na pasta Resources de um componene serão carregados por esse componente.
In a host project containing one or more components, each component as well as the host projects has its own “resources string.” Resources are partitioned between the different projects: it is not possible to access the resources of component A from component B or the host project.
Executing initialization code
A component can execute 4D code automatically when opening or closing the host database, for example in order to load and/or save the preferences or user states related to the operation of the host database.
Executing initialization or closing code is done by means of the
On Host Database Event database method.
For security reasons, you must explicitly authorize the execution of the
On Host Database Eventdatabase method in the host database in order to be able to call it. For security reasons, you must explicitly authorize the execution of the
On Host Database Eventdatabase method in the host database in order to be able to call it.
Proteção dos componentes: compilação
By default, all the code of a matrix project installed as a component is potentially visible from the host project. Em particular:
- The shared project methods are found on the Methods Page of the Explorer and can be called in the methods of the host project. Seu conteúdo pode ser selecionado e copiado na área de vista prévia do Explorador. Também podem ser vistos no depurador. However, it's not possible to open them in the Code Editor or modify them.
- The other project methods of the matrix project do not appear in the Explorer but they too can be viewed in the debugger of the host project.
- The non-hidden classes and functions can be viewed in the debugger if a namespace is declared.
To protect the code of a component effectively, simply compile and build the matrix project and provide it in the form of a .4dz file. When a compiled matrix project is installed as a component:
- The shared project methods, classes and functions can be called in the methods of the host project. Shared project methods are also visible on the Methods Page of the Explorer. However, their contents will not appear in the preview area and in the debugger.
- The other project methods of the matrix project will never appear.
We encourage you to support the 4D developer community by sharing your components, preferably on the GitHub platform. We recommend that you use the
4d-component topic to be correctly referenced.