《Unity虚拟现实技术及其应用》 课件 19 Enumeration and Iterators

UsingSystem.Collection.Generic;staticvoidMain(string[]args)

{List<int>int_list=newList<int>(10);int_list.Add(0);int_list.Add(1);int_list.Add(2);foreach(intiinint_list)Console.WriteLine(i);

}Enumeration(枚举)Anenumerator(计数器)isaread-only,forward-onlycursoroverasequenceofvalues(collection集合).AnenumeratorisanobjectthatimplementsSystem.Collections.IEnumeratororSystem.Collections.Generic.IEnumerator<T>DefineacustomcollectiontosupportforeachThecustomcollectionshouldbederivedfromIEnumerable,andimplement：publicIEnumeratorGetEnumerator()YoushouldprovideacustomEnumeratorforthecustomcollection,andimplementMoveNext(),Reset(),Current,publicclassPerson{publicPerson(stringfName,stringlName){this.firstName=fName;this.lastName=lName;}publicstringfirstName;publicstringlastName;}CollectionofPersonobjectspublicclassPeople:IEnumerable

{privatePerson[]_people;publicPeople(Person[]pArray)

{_people=newPerson[pArray.Length];for(inti=0;i<pArray.Length;i++)

{_people[i]=pArray[i];}

}IEnumeratorIEnumerable.GetEnumerator(){//！！！！return(IEnumerator)GetEnumerator();

}publicPeopleEnumGetEnumerator(){//！！！！returnnewPeopleEnum(_people);

}

}实现IEnumeratorpublicclassPeopleEnum:IEnumerator{

publicPerson[]_people;

intposition=-1;

publicPeopleEnum(Person[]list){_people=list;}

publicboolMoveNext(){position++;return(position<_people.Length);}

publicvoidReset(){position=-1;}

objectIEnumerator.Current{get{returnCurrent;}}

publicPersonCurrent{get{return_people[position];}}

}staticvoidMain(string[]args)

{Person[]pArray=newPerson[3]

{newPerson("DF","Liu"),newPerson("KK","LEE"),newPerson("YY","WANG"),

};PeoplepList=newPeople(pArray);foreach(PersonpinpList)

{Console.WriteLine(p.firstName+""+p.lastName);

}

}yieldWhenyouusetheyieldcontextualkeywordinastatement,youindicatethatthemethod,operator,orgetaccessorinwhichitappearsisaniterator(enumerator).publicclassPowersOf2{staticvoidMain(){//Displaypowersof2uptotheexponentof8:

foreach(intiinPower(2,8)){Console.Write("{0}",i);}

}publicstaticIEnumerable<int>Power(intnumber,intexponent)

{intresult=1;

for(inti=0;i<exponent;i++){result=result*number;yieldreturnresult;}}

}//Output:248163264128256

}publicclassGalaxy{publicStringName{get;set;}publicintMegaLightYears{get;set;}}publicclassGalaxies{publicIEnumerable<Galaxy>NextGalaxy{get{yieldreturnnewGalaxy{Name="Tadpole",MegaLightYears=400};yieldreturnnewGalaxy{Name="Pinwheel",MegaLightYears=25};yieldreturnnewGalaxy{Name="MilkyWay",MegaLightYears=0};yieldreturnnewGalaxy{Name="Andromeda",MegaLightYears=3};}}}publicstaticvoidShowGalaxies(){vartheGalaxies=newGalaxies();foreach(GalaxytheGalaxyintheGalaxies.NextGalaxy){Debug.WriteLine(theGalaxy.Name+""+theGalaxy.MegaLightYears.ToString());}}AnotherexampleforMultipleyieldStatementsstaticvoidMain(){foreach(stringsinFoo())Console.Write(s+"");//OneTwoThree}staticIEnumerable<string>Foo(){yieldreturn"One";yieldreturn"Two";yieldreturn"Three";}UsingyieldbreakstaticIEnumerable<string>Foo(boolb)

{yieldreturn"one";yieldreturn"two";if(b)yiel