![]() ![]() All the units you refer to must be present in the project directory or in a directory of the search path (you can set the search path for a project in the Directories/Conditionals page of the project’s Options dialog box).Ĭ++ programmers should be aware that the uses statement does not correspond to an include directive. When you need to refer to other units from the code of the routines and methods, you should add elements in this second uses clause instead of the first one. The second uses clause, at the beginning of the implementation section, indicates more units we need to access only in the implementation code. This includes the units that define the data types we refer to in the definition of other data types, such as the components used within a form we are defining. ![]() The uses clause at the beginning of the interface section indicates which other units we need to access in the interface portion of the unit. Initialization // optional initialization part finalization // optional clean-up code end. all the exported functions must be coded procedure MyProc īegin //. list of exported functions and procedures procedure MyProc Interface // other units we need to refer to uses The general structure of a unit, with all its possible sections, is the following: Finally, the unit can have an optional initialization section with some startup code, to be executed when the program is loaded into memory it can also have an optional finalization section, to be executed on program termination. A unit has a unique name corresponding to its filename, an interface section declaring what is visible to other units, and an implementation section with the real code and other hidden declarations. This blank unit contains the following code, delimiting the sections a unit is divided into: By selecting the File > New menu command and then the Unit icon in the New page of the Object Repository, you add a new blank unit to the current project. Units do not need to define forms they can simply define and make available a collection of routines. When you add a new form to a project (with the corresponding toolbar button or the File > New Form menu command), Delphi actually adds a new unit, which defines the class for the new form.Īlthough every form is defined in a unit, the reverse is not true. In a Delphi application, every form has a corresponding unit behind it. Units, in fact, were the basis of the modularity in the language before classes were introduced. The cover of the 4th edition of Essential Pascal,ĭelphi applications make intensive use of units, or program modules. ![]() The "backing" field of a property is almost always private, since the idea of a property is to encapsulate all outside access to it.Essential Pascal on Marco Web Center Make it a function, not a property, if using it has a side effect or returns something random. The value of the property should not change unexpectedly. Again, the good convention is to make it behave like a constant, at least constant for this object instance with this state. The read-only properties are often used to make some field read-only from the outside. The idea is that after M圜lass.MyProperty := 123 the programmer can expect that M圜lass.MyProperty = 123. Do not convert or scale the requested value. Do not reject invalid values silently in the "setter" (raise an exception if you must). The setter function should always set the requested value, such that calling the getter yields it back. This is in fact one of the cool possibilities of a "getter" function. Note that it’s OK for getter to have some invisible side-effect, for example to cache a value of some calculation (known to produce the same results for given instance), to return it faster next time. Using COM interfaces with reference-counting disabled More stuff inside classes and nested classes Callbacks (aka events, aka pointers to functions, aka procedural variables) Containers (lists, dictionaries) using generics How the exceptions are displayed by various libraries Finally (doing things regardless if an exception occurred) Free notification observer (Castle Game Engine) Virtual methods, override and reintroduce Exposing one unit identifiers from another Enumerated and ordinal types and sets and constant-length arrays Testing single expression for multiple values (case) Logical, relational and bit-wise operators ![]()
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