OOP(C )_第2章_C 初探：创建和使用对象(最终版).ppt

第二章C 初探 创建和使用对象 面向对象程序设计 C ThischapterexplainskeydifferencesbetweenCandC andtakesyouthroughthreeessentialC features Typesafety 类型安全性 Classes 类 抽象 封装 多态性等 Templates 模板 AlsocoveredareIOStreamsandthefreestoreoperatorsnewanddelete 2 1概述 2 1概述 cont HistoryChangestoCsubsetIOStreamsnewanddeleteObjectsTemplates 2 2C 的历史 BjarneStroustrup BellLabs 1980s CwithClassesAddobjectstoCLeverageC sefficiency 效率 portability 轻巧性 availability 可用性 ANSICommittee 1991ISOStandard July1998 2 3对C子集的某些改进 Motivatedmostlybytypesafety a ischar notint c a isconstchar notchar c f isthesameasf void 而在C中等同于参数个数不确定的函数constintegerscanbeusedasarraydimensions常量在C 中通常是一个符号表中的条目 而在C中是一个变量 Structuretagsaretypenames Abstract 抽象 Encapsulation 封装 AccessControl Public Private Protected Friends 友元 允许友元破坏封装性Inheritance 继承 VirtualFunction 多态性 LaterBinding 晚绑定 Overloading 重载 允许函数名和运算符重载Template 模板 2 4对C的扩展 2 5C 的输入输出 IOStreams初探 hello cpp includeusingnamespacestd intmain cout Hello world endl Hello world 8 cout是一个预定义的对象 cout Hello world 等价于 cout operator Hello world C 的输入输出是类型安全的输入输出 取代printf 2 6newanddelete运算符 Replacementformalloc freeint ip newint 7 deleteip 2 7对象 Object 概述 BasedonClassesstructswithmemberfunctionsAlwayshaveanassociatedobjectImprovedsupportforinformationhidingprivate protectedkeywordsAutomaticinitialization cleanup 构造和析构函数 2 7 1例 ClassStack intstack h AStackclassforintsclassStackOfInt public StackOfInt int 构造函数 生成对象时自动执行voidpush int intpop inttop const intsize const StackOfInt 析构函数 撤销对象时自动执行private int data intlength intptr intstack cpp include intstack h StackOfInt StackOfInt intstk size data newint length stk size ptr 0 voidStackOfInt push intx if ptr0 returndata ptr elsethrow underflow intstack cppcontinued intStackOfInt top const if ptr 0 returndata ptr 1 elsethrow underflow intStackOfInt size const returnptr StackOfInt StackOfInt delete data 输出 43210 tintstack cpp TestsStackOfInt include intstack h includeusingnamespacestd intmain constintN 5 StackOfIntstk N for inti 0 i0 cout stk pop cout endl 2 8Templates 模板 参数化的类 SupportgenericprogrammingIdealforcontainersLogicisindependentfromcontainedobjectsYouwritethetemplatecodeonceCompilergeneratesversionsondemand 例 通用栈模板 stack9b h AStacktemplatetemplateclassStack public Stack int voidpush T Tpop Ttop const intsize const Stack private T data intlength intptr templateStack Stack intstk size data newT length stk size ptr 0 templatevoidStack push Tx if ptrTStack pop if ptr 0 returndata ptr elsethrow underflow templateTStack top const if ptr 0 returndata ptr 1 elsethrow underflow tstack9b cpp TeststheStacktemplate include stack9b h includeusingnamespacestd intmain constintN 5 Stackstk N for inti 0 i0 cout stk pop cout endl 输出 4 53 52 51 50 5 2 9小结 AFirstLookatC C emphasizestypesafetyIOStreamsprovidetype safeI Onewanddeleteprovidesafeheap 堆 managementClas