IOS 常用字串的操作
IOS 常用字串的操作
不可變字串
將NSData轉化為NSString
NSString* str = [[NSString alloc] initWithData:response encoding:NSUTF8StringEncoding];
將NSString 轉化為NSData
- (NSData *)dataUsingEncoding:(NSStringEncoding)encoding;
載一個字串中刪除一個字元或字串
[_display deleteCharactersInRange:NSMakeRange(index_of_char_to_remove, 1)];
數學轉換為字串
NSString *returnStr;
returnStr = [[NSNumber numberWithInt:row] stringValue];
建立字串的方法
1、建立常量字串。
NSString *astring = @"This is a String!";
2、建立空字串，給予賦值.
NSString *astring = [[NSString alloc] init];
astring = @"This is a String!";
[astring release];
NSLog(@"astring:%@",astring);
3、在以上方法中，提升速度:initWithString方法
NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
NSLog(@"astring:%@",astring);
[astring release];
4、用標準c建立字串:initWithCString方法
char *Cstring = "This is a String!";
NSString *astring = [[NSString alloc] initWithCString:Cstring];
NSLog(@"astring:%@",astring);
[astring release];
5、建立格式化字串:佔位符（由一個%加一個字元組成）
int i = 1;
int j = 2;
NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];
NSLog(@"astring:%@",astring);
[astring release];
6、建立臨時字串
NSString *astring;
astring = [NSString stringWithCString:"This is a temporary string"];
NSLog(@"astring:%@",astring);
從檔案讀取字串:initWithContentsOfFile方法
NSString *path = @"astring.text";
NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
NSLog(@"astring:%@",astring);
[astring release];
寫字串到檔案:writeToFile方法
NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
NSLog(@"astring:%@",astring);
NSString *path = @"astring.text";
[astring writeToFile: path atomically: YES];
[astring release];
比較兩個字串
1、用C比較:strcmp函式
char string1[] = "string!";
char string2[] = "string!";
if(strcmp(string1, string2) = = 0)
{
NSLog(@"1");
}
2、isEqualToString方法
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 isEqualToString:astring02];
NSLog(@"result:%d",result);
3、compare方法(comparer返回的三種值)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
4、NSOrderedSame判斷兩者內容是否相同
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
NSLog(@"result:%d",result);
5、NSOrderedAscending判斷兩物件值的大小(按字母順序進行比較，astring02大於astring01為真)
NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;
NSLog(@"result:%d",result);
6、NSOrderedDescending判斷兩物件值的大小(按字母順序進行比較，astring02小於astring01為真)
-
不考慮大小寫比較字串1
NSString *astring01 = @"this is a String!"; NSString *astring02 = @"This is a String!"; BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame; NSLog(@"result:%d",result);
7、NSOrderedDescending判斷兩物件值的大小(按字母順序進行比較，astring02小於astring01為真)
-
不考慮大小寫比較字串2
NSString *astring01 = @"this is a String!"; NSString *astring02 = @"This is a String!"; BOOL result = [astring01 compare:astring02 options:NSCaseInsensitiveSearch | NSNumericSearch] = = NSOrderedSame; NSLog(@"result:%d",result);
NSCaseInsensitiveSearch:不區分大小寫比較 NSLiteralSearch:進行完全比較，區分大小寫 NSNumericSearch:比較字串的字元個數，而不是字元值。
1、改變字串的大小寫
NSString *string1 = @"A String";
NSString *string2 = @"String";
NSLog(@"string1:%@",[string1 uppercaseString]);//大寫
NSLog(@"string2:%@",[string2 lowercaseString]);//小寫
NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小
2、在串中搜尋子串
NSString *string1 = @"This is a string";
NSString *string2 = @"string";
NSRange range = [string1 rangeOfString:string2];
int location = range.location;
int leight = range.length;
NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i",location,leight]];
NSLog(@"astring:%@",astring);
[astring release];
3、抽取子串
-substringToIndex: 從字串的開頭一直擷取到指定的位置，但不包括該位置的字元
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringToIndex:3];
NSLog(@"string2:%@",string2);
-substringFromIndex: 以指定位置開始（包括指定位置的字元），幷包括之後的全部字元
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringFromIndex:3];
NSLog(@"string2:%@",string2);
-substringWithRange: //按照所給出的位置，長度，任意地從字串中擷取子串
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
NSLog(@"string2:%@",string2);
4、擴充套件路徑
NSString *Path = @"~/NSData.txt";
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);
5、副檔名
NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);
可變字串
1、給字串分配容量
stringWithCapacity:
NSMutableString *String;
String = [NSMutableString stringWithCapacity:40];
2、在已有字串後面新增字元
appendString: and appendFormat:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
//[String1 appendString:@", I will be adding some character"];
[String1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]];
NSLog(@"String1:%@",String1);
3、在已有字串中按照所給出範圍和長度刪除字元
//deleteCharactersInRange:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 deleteCharactersInRange:NSMakeRange(0, 5)];
NSLog(@"String1:%@",String1);
4、在已有字串後面在所指定的位置中插入給出的字串
//-insertString: atIndex:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 insertString:@"Hi! " atIndex:0];
NSLog(@"String1:%@",String1);
5、將已有的空符串換成其它的字串
//-setString:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 setString:@"Hello Word!"];
NSLog(@"String1:%@",String1);
6、按照所給出的範圍，和字串替換的原有的字元
//-setString:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];
NSLog(@"String1:%@",String1);
7、判斷字串內是否還包含別的字串(字首，字尾)
01：檢查字串是否以另一個字串開頭- (BOOL) hasPrefix: (NSString *) aString;
NSString *String1 = @"NSStringInformation.txt";
[String1 hasPrefix:@"NSString"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");
[String1 hasSuffix:@".txt"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");
02：查詢字串某處是否包含其它字串 - (NSRange) rangeOfString: (NSString *) aString，這一點前面在串中搜尋子串用到過;
NSArray
建立數
//NSArray *array = [[NSArray alloc] initWithObjects:
@"One",@"Two",@"Three",@"Four",nil];
self.dataArray = array;
[array release];
//- (unsigned) Count;陣列所包含物件個數；
NSLog(@"self.dataArray cound:%d",[self.dataArray count]);
//- (id) objectAtIndex: (unsigned int) index;獲取指定索引處的物件;
NSLog(@"self.dataArray cound 2:%@",[self.dataArray objectAtIndex:2]);
從一個陣列拷貝資料到另一陣列(可變數級)
1、arrayWithArray:
//NSArray *array1 = [[NSArray alloc] init];
NSMutableArray *MutableArray = [[NSMutableArray alloc] init];
NSArray *array = [NSArray arrayWithObjects: @"a",@"b",@"c",nil];
NSLog(@"array:%@",array);
MutableArray = [NSMutableArray arrayWithArray:array];
NSLog(@"MutableArray:%@",MutableArray);
array1 = [NSArray arrayWithArray:array];
NSLog(@"array1:%@",array1);
2、Copy
//id obj;
NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects: @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
NSLog(@"oldArray:%@",oldArray);
for(int i = 0; i < [oldArray count]; i++)
{
obj = [[oldArray objectAtIndex:i] copy];
[newArray addObject: obj];
}
NSLog(@"newArray:%@", newArray);
[newArray release];
3、快速列舉
//NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects:@"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
NSLog(@"oldArray:%@",oldArray);
for(id obj in oldArray)
{
[newArray addObject: obj];
}
NSLog(@"newArray:%@", newArray);
[newArray release];
4、Deep copy
//NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects: @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
NSLog(@"oldArray:%@",oldArray);
newArray = (NSMutableArray*)CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (CFPropertyListRef)oldArray, kCFPropertyListMutableContainers);
NSLog(@"newArray:%@", newArray);
[newArray release];
5、Copy and sort
//NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects: @"b",@"a",@"e",@"d",@"c",@"f",@"h",@"g",nil];
NSLog(@"oldArray:%@",oldArray);
NSEnumerator *enumerator;
enumerator = [oldArray objectEnumerator];
id obj;
while(obj = [enumerator nextObject])
{
[newArray addObject: obj];
}
[newArray sortUsingSelector:@selector(compare:)];
NSLog(@"newArray:%@", newArray);
[newArray release];
切分陣列
1、從字串分割到陣列－ componentsSeparatedByString:
NSString *string = [[NSString alloc] initWithString:@"One,Two,Three,Four"];
NSLog(@"string:%@",string);
NSArray *array = [string componentsSeparatedByString:@","];
NSLog(@"array:%@",array);
[string release];
2、從陣列合並元素到字串- componentsJoinedByString:
NSArray *array = [[NSArray alloc] initWithObjects:@"One",@"Two",@"Three",@"Four",nil];
NSString *string = [array componentsJoinedByString:@","];
NSLog(@"string:%@",string);
NSMutableArray
給陣列分配容量
NSArray *array;
array = [NSMutableArray arrayWithCapacity:20];
在陣列末尾新增物件
- (void) addObject: (id) anObject;
//NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
[array addObject:@"Four"];
NSLog(@"array:%@",array);
刪除陣列中指定索引處物件
-(void) removeObjectAtIndex: (unsigned) index;
//NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
[array removeObjectAtIndex:1];
NSLog(@"array:%@",array);
陣列列舉
- (NSEnumerator *)objectEnumerator;從前向後
//NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
NSEnumerator *enumerator;
enumerator = [array objectEnumerator];
id thingie;
while (thingie = [enumerator nextObject]) {
NSLog(@"thingie:%@",thingie);
}
- (NSEnumerator *)reverseObjectEnumerator;從後向前
//NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
NSEnumerator *enumerator;
enumerator = [array reverseObjectEnumerator];
id object;
while (object = [enumerator nextObject]) {
NSLog(@"object:%@",object);
}
快速列舉
//NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
for(NSString *string in array
{
NSLog(@"string:%@",string);
}
NSDictionary
建立字典
- (id) initWithObjectsAndKeys;
//NSDictionary *dictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"One",@"1",@"Two",@"2",@"Three",@"3",nil];
NSString *string = [dictionary objectForKey:@"One"];
NSLog(@"string:%@",string);
NSLog(@"dictionary:%@",dictionary);
[dictionary release];
NSMutableDictionary
建立可變字典
1、建立
NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
2、新增字典
[dictionary setObject:@"One" forKey:@"1"];
[dictionary setObject:@"Two" forKey:@"2"];
[dictionary setObject:@"Three" forKey:@"3"];
[dictionary setObject:@"Four" forKey:@"4"];
NSLog(@"dictionary:%@",dictionary);
3、刪除指定的字典
[dictionary removeObjectForKey:@"3"];
NSLog(@"dictionary:%@",dictionary);
NSValue（對任何物件進行包裝）
將NSRect放入NSArray中
1、將NSRect放入NSArray中
NSMutableArray *array = [[NSMutableArray alloc] init];
NSValue *value;
CGRect rect = CGRectMake(0, 0, 320, 480);
value = [NSValue valueWithBytes:&rect objCType:@encode(CGRect)];
[array addObject:value];
NSLog(@"array:%@",array);
2、從Array中提取
value = [array objectAtIndex:0];
[value getValue:&rect];
NSLog(@"value:%@",value);
3、從目錄搜尋副檔名為jpg的檔案
//NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *home;
home = @"../Users/";
NSDirectoryEnumerator *direnum;
direnum = [fileManager enumeratorAtPath: home];
NSMutableArray *files = [[NSMutableArray alloc] init];
4、列舉
NSString *filename;
while (filename = [direnum nextObject]) {
if([[filename pathExtension] hasSuffix:@"jpg"]){
[files addObject:filename];
}
}
5、快速列舉
for(NSString *filename in direnum)
{
if([[filename pathExtension] isEqualToString:@"jpg"]){
[files addObject:filename];
}
}
NSLog(@"files:%@",files);
4.1列舉
NSEnumerator *filenum;
filenum = [files objectEnumerator];
while (filename = [filenum nextObject]) {
NSLog(@"filename:%@",filename);
}
5.1快速列舉
for(id object in files)
{
NSLog(@"object:%@",object);
}
#import <Foundation/Foundation.h>
int main (int argc, const char * argv[]) {
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
//建立字串
NSString *height;
/**類方法：
* +(id) stringWithFormat: (NSString *) format,...
* 通過格式字串和引數來建立NSString
* 省略號（。。。）：可以接受多個以逗號分割的引數。
* 這宣告方法時新增加號（＋），那麼這個方法為類方法，不需要建立例項就可以呼叫，通常用於建立心的例項，我們稱用來建立新物件的類方法為工廠方法。
* objective－c執行時生成一個類的時候，它會建立一個代表該類的類物件。類物件包含了指向超類的指標，類名，和指向類方法列表的指標。類物件還包含一個long型資料，為新建立的類例項物件指定大小（以位元組為單位）
* 類方法可以用來訪問全域性資料。
* 例項方法要用前導減號（－）來開始宣告
*/
height=[NSString stringWithFormat:@"you heigh is %d feet,%d inches",5,11];
NSLog(height);
//length 返回字串中字元的個數。－（unsigned int) length;
if([height length]>5){
NSLog(@"height length ------");
}
//字串比較
/**
* isEqualToString :可以用來比較接收方和當作引數傳遞來的字串的內容是否相同，返回yes和no
*/
NSString *thing1=@"hello";
NSString *thing2=[[NSString alloc] initWithString:@"hello"];
if([thing1 isEqualToString:thing2]){
NSLog(@"they are same");
}
/**
* ==:只判斷指標數值，而不是它們所指向的內容
*/
if(thing1==thing2){
NSLog(@"== same");
}
/*
* compare:比較兩個字串。區分大小寫
* compare將接收物件和傳遞來的字串逐個字元的進行比較，它返回一個NSComparisonResult(列舉型別)來顯示結果。
* typedef enum _NSComparisonResult{
* NSOrderedAscending=-1;
* NSOrderedsame;
* NSOrderedDescending;
* }
* NSComparisonResult;
*/
[thing1 compare:thing2];
if(NSOrderedSame==[thing1 compare:thing2]){
NSLog(@"compare same");
}
//compare：options:
/***
* -(NSComparisonResult) compare:(NSString *) string
* options:(unsinged) mask;
*
* options 是一個位掩碼，可以使用|新增選項標記
* 選項：
* NSCaseInsensitiveSearch:不區分大小寫字元
* NSLiteralSearch:進行完全比較，區分大小寫
* NSNumbericSearch:比較字串的字元個數，而不是字元值
*/
if([thing1 compare:thing2 options:NSCaseInsensitiveSearch| NSNumericSearch]==NSOrderedSame)
{
NSLog(@"they match");
}
/**
* 以某個字串開始或結尾
* -(BOOL) hasPrefix:(NSString *) aString;
* -(BOOL) hasSuffix:(NSString *) aString;
*/
NSString *fileName=@"aabbbcc";
if([fileName hasPrefix:@"aa"])
{
NSLog(@"begin with aa");
}
if([fileName hasSuffix:@"cc"])
{
NSLog(@"end with cc");
}
//NSMutableString 可變字串
//SString 是不可變的，一旦NSString 被建立了，我們就不能改變它。
//+(id) stringWithCapacity:(unsinged) capacity; capacity:是給NSMutableString的一個建議，字串的大小並不侷限於所提供的大小，這個容量僅是個最優值。
NSMutableString *str=[NSMutableString stringWithCapacity:40];
[str appendFormat:@"sdfsdf%d",5];
[str appendString:@"ssssssss"];
NSLog(str);
//刪除字串
//-(void) deleteCharactersInRange:(NSRange) range;
NSMutableString *ms;
ms=[NSMutableString stringWithCapacity:50];
[ms appendString:@"aabbccdd"];
NSRange range;
range=[ms rangeOfString:@"cc"];
[ms deleteCharactersInRange:range];
NSLog(ms);
//與例項方法一樣，繼承對類方法也同樣適用
//------------------集合－－－－－－－－－－－－－－
//NSArray ,NSDictionary
/**
* NSArray 是一個cocoa類，用來儲存物件的有序列表。
* NSArray有兩個限制：1，它只能儲存objective－c的物件，而不能儲存c語言中的基本資料型別如int，float，enum，struct，或者nsarray中的隨機指標。2，不能這nsarray中儲存nil
* 類方法：
* arrayWithObjects:建立一個新的nsarray。傳送一個以逗號分割的物件列表，這列表結尾新增nil代表列表結束，（這就是不能這nsarray中儲存nil的原因）
*/
NSArray *array=[NSArray arrayWithObjects:@"aa",@"bb",@"cc",nil];
//-(unsigned) count; 取得包含物件的個數
//-(id) objectAtIndex:(unsigned int) index; 取得索引位置的物件
int i;
for (i=0; i<[array count]; i++)
{
NSLog(@"index %d has %@",i,[array objectAtIndex:i]);
}
//------------切分陣列
//-componentsSeparatedByString:
NSString *ns=@"sdf,dsfs,dfd,fdf,df,dd";
NSArray *comArr=[ns componentsSeparatedByString:@","];
for(int i=0;i<[comArr count];i++){
NSLog(@"componentsSeparatedByString===%@",[comArr objectAtIndex:i]);
}
//componentJoinedByString: 合併nsarray中的元素來建立字串
NSString *joinedStr=[comArr componentsJoinedByString:@"-->"];
NSLog(@"joined---= %@",joinedStr);
//可變陣列
NSMutableArray *mutableArr=[NSMutableArray arrayWithCapacity:40];
[mutableArr addObject:@"aa"];
[mutableArr addObject:@"bb"];
[mutableArr addObject:@"cc"];
[mutableArr addObject:@"dd"];
for(int i=0;i<[mutableArr count];i++)
{
NSLog(@"mutableArr==%@",[mutableArr objectAtIndex:i]);
}
//----- -(void) removeObjectAtIndex:(unsinged) index; 刪除指定索引的物件,
//刪除一個物件之後，陣列中並沒有留下漏洞，被刪除物件後面的陣列元素的哦被前移來填補空缺
[mutableArr removeObjectAtIndex:2];
for(int i=0;i<[mutableArr count];i++){
NSLog(@"removeObjectAtIndex == %@",[mutableArr objectAtIndex:i]);
}
//列舉
//NSEnumerator ,它是cocoa用來描述這種集合迭代運輸的方法
//-(NSEnumerator *) objectEnumerator;
NSEnumerator *enumerator=[mutableArr objectEnumerator];
id thingie;
while(thingie=[enumerator nextObject])
{
NSLog(@"i found %@",thingie);
}
//快速列舉
for(NSString *string in mutableArr){
NSLog(@"for in == %@",string);
}
//NSDictionary 字典
/*
* NSDictionary 是在給定的關鍵字（通常是一個NSString字串）下儲存一個數值（可以是任何型別的物件）。然後你可以用這個關鍵字來查詢相應的數值。
* NSDictionary 是鍵查詢的優化儲存方式。它可以立即找出要查詢的資料，而不需要遍歷整個陣列進行查詢。
* ＋（id) dictionaryWithObjectAndKeys:(id) firstObject,....;
* 該方法接收物件和關鍵字交替出現的系列，以nil值作為終止符號。
*/
NSDictionary *dic=[NSDictionary dictionaryWithObjectsAndKeys:@"aaa",@"a",@"bbb",@"b",nil];
NSString *dicStr=[dic objectForKey:@"a"];
if([dicStr isEqualToString:@"aaa"]){
NSLog(@"------------00000000000000000");
}
//可變字典
NSMutableDictionary *mutableDic=[NSMutableDictionary dictionaryWithCapacity:50];
[mutableDic setObject:@"1111" forKey:@"1"];
[mutableDic setObject:@"222" forKey:@"2"];
//刪除 -(void) removeObjectForKe:(id) key;
[mutableDic removeObjectForKey:@"2"];
NSArray *keyArr=[mutableDic allKeys];
for(NSString *str in keyArr){
NSLog(@"key== %@",str);
NSLog(@"value== %@",[mutableDic objectForKey:str]);
}
//各種數值，NSNumber NSValue
/*
* cocoa 提供了NSNumber類來包裝基本資料型別
* +(NSNumber *) numberWithChar:(char) value;
* +(NSNumber *) numberWithInt:(int) value;
* +(NSNumber *) numberWithFloat:(float) value;
* +(NSNumber *) numberWthiBool:(BOOL) value;
* -(char) charValue;
* -(int) intVlaue;
* -(float) floatValue;
* -(BOOL) boolValue;
* -(NSString *) stringValue;
**/
NSNumber *number;
number=[NSNumber numberWithInt:3];
[mutableDic setObject:number forKey:@"int"];
int num=[[mutableDic objectForKey:@"int"] intValue];
NSLog(@"int object value== %d",num);
//NSValue .NSNumber實際上是NSValue的子類，NSValue可以包裝任意值
/**
* +(NSValue *) valueWithBytes:(const void *) value objCType:(const char *) type;
* 傳遞的引數是你想要包裝的數值的地址，通常，得到的是你想要儲存的變數的地址（在c語言裡適用操作符 & ），你也可以提供一個描述這個資料型別的字串，通常用來說明struct中實體的型別和大小。你不用自己寫程式碼
* 來生成這個字串，@encode編譯器指令可以接受資料型別的名稱併為你生成合適的字串
*/
NSRect rect= NSMakeRect(1, 2, 30, 40);
NSValue *value;
value=[NSValue valueWithBytes:&rect objCType:@encode(NSRect)];
NSMutableArray *mr=[NSMutableArray arrayWithCapacity:50];
[mr addObject:value];
//getValue 提取資料
/**
* -(void) getValue:(void *) value; 要傳遞的是儲存這個數值的變數的地址
*/
/***
* value=[mr objectAtIndex:0];
* NSRect r;
* NSLog(@"00000 ===%@",r);
* [value getValue:&r];
* NSLog(@"111== %@",r);
*/
/**
* �+(NSValue *) valueWithPoint:(NSPoint) point;
* +(NSValue *) valueWithSize:(NSSize) size;
* +(NSValue *) valueWithRect:(NSRect) rect;
* -(NSPoint) pointValue;
* -(NSSize) sizeValue;
* -(NSRect) rectValue;
*/
//NSNull
/*
* +(NSNull *) null;
*/
[mutableDic setObject:[NSNull null] forKey:@"fax"];
id fax;
fax=[mutableDic objectForKey:@"fax"];
if(fax==[NSNull null]){
NSLog(@"pppppppppppppppppp");
}
[pool drain];
return 0;
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