计算机专业外文翻译.pdf

计算机专业外文翻译

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TheDelphiProgrammingLanguage

TheDelphidevelopmentenvironmentisbasedonanobject-oriented

extensionofthe

PcisealprogramminglanguageknownasObjectPascal.ostmodern

programminglanguages

supportobject-orientedprogramming(OOP).OOPlanguagesarebased

onthreefundamental

concepts:encapsulation(usuallyimplementedwithclasses),

inheritance,andpolymorphism

(orlatebinding).

IClassesandObjects

DelphiisbasedonOOPconcepts,andinparticularonthedefinition

ofnewclasstypes.

TheuseofOOPispartiallyenforcedbythevisualdevelopment

environment,becausefor

everynewformdefinedatdesigntime,Delphiautomatical1ydefines

anewclass.Inaddition,

everycomponentvisuallyplacedonaformisanobjectofaclass

typeavailableinoraddedto

thesystemlibrary.

AsinmostothermodernOOPlanguages(includingJavaandC#),in

Delphiaclass-type

variabledoesn*tprovidethestorageortheobject,butisonlya

pointerorreerencetothe

objectinmemory.Beoreyouusetheobject,youmustallocate

memoryoritbycreatinga

newinstanceorbyassigninganexistinginstancetothevariable:

var

Objl,0bj2:TMyClass;

begin//assignanewlycreatedobject

Objl:=TMyClass.Create;//assigntoanexistingobject

Obj2:=ExistingObject;

ThecalltoCreateinvokesadeaultconstructoravailableorevery

class,unlesstheclass

redeinesit(asdescribedlater).Todeclareanewclassdatatype

inDelphi,withsomelocal

dataieldsandsomemethods,usetheollowingsyn