[转] 用法总结：NSNumber、NSString、NSDat

作者: 土豆卡 | 来源:发表于2016-06-23 14:16 被阅读177次

在网上看到的，感觉可以，转过来整理了一下。

NSNumber

    +(NSNumber *)numberWithInt:(int)value;
    +(NSNumber *)numberWithDouble:(double)value;
    -(int)intValue;
    -(double)doubleValue;

NSNumber可以将基本数据类型包装起来，形成一个对象，这样就可以给其发送消息，装入NSArray中等等。

    NSNumber * intNumber=[NSNumber numberWithInt：100]；
    NSNumber *floatNumber=[NSNUmber
    numberWithFloat:100.00];
    int i=[intNumber intValue];
    if([intNumber isEqualToNumber:floatNumber]) ....

NSNumber继承NSObject ，可以使用比较 compare： isEqual等消息

NSString

一个NSString对象可以存储一段Unicode字符。在cocoa中，所有和字符、字符串相关的处理都是使用NSString来完成。

    NSObject -> NSString     // NSString继承自NSObject
    +(id) stringWithContentsOfFile:path encoding:enc error:err;
    +(id) stringWithContentsOfURL:url encoding:enc error:err;
    +(id) stringWithString:nsstring;   //创建一个新的字符串，并将其设置为nsstring

    -(id)initWithFormat:(NSString *)format, ...  ;
    -(id)initWithString:nsstring;     //将分配的字符串设置为nsstring
    -(BOOL)isEqualToString:(NSString *)string;
    -(BOOL)hasPrefix:(NSString *)string;
    -(int)intValue;
    -(double)doubleValue;

    -(NSString *)stringByAppendingString:(NSString *)string;  // 给一个字符串附加一个字符串string。
    -(NSString *)stringByAppendingFormat:(NSString *)string;
    -(NSString *)stringByDeletingPathComponent;

创建字符串的方法

1、创建常量字符串

    NSString *astring = @"This is a String!";

2、先创建一个空的字符串，然后赋值；
alloc和init组合则适合在函数之间传递参数，用完之后需要手工release

    NSString *astring = [[NSString alloc] init];
    astring = @"This is a String!";
    NSLog(@"astring:%@",astring);
    [astring release];

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、创建临时字符串

    NSString *astring;
    astring = [NSString stringWithCString:"This is a temporary string"];
    NSLog(@"astring:%@",astring);
    OR
    NSString *  scriptString = [NSString stringWithString:@" tell application \"Mail\"\r"];

5、创建格式化字符串:占位符（由一个%加一个字符组成）

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];

从文件读取字符串

NSString *path = @"astring.text";
NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
NSLog(@"astring:%@",astring);
[astring release];

写字符串到文件

NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
NSLog(@"astring:%@",astring);
NSString *path = @"astring.text";   
[astring writeToFile: path atomically: YES];
[astring release];

比较两个字符串

1、用C比较:strcmp函数

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返回的三种值：NSOrderedSame，NSOrderedAscending，NSOrderedDescending)

NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";   
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;   //NSOrderedSame 判断两者内容是否相同
NSLog(@"result:%d",result);   

NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;   
NSLog(@"result:%d",result);
//NSOrderedAscending 判断两对象值的大小(按字母顺序进行比较，astring02大于astring01为真)

NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;   
NSLog(@"result:%d",result);     
//NSOrderedDescending 判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)

4、不考虑大小写比较字符串1

NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;   
NSLog(@"result:%d",result);     
//NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)

5、不考虑大小写比较字符串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:不区分大小写比较 NSLiteralSearch:进行完全比较，区分大小写 NSNumericSearch:比较字符串的字符个数，而不是字符值。

改变字符串的大小写

NSString *string1 = @"A String";
NSString *string2 = @"String";
NSLog(@"string1:%@",[string1 uppercaseString]);//uppercaseString返回转换为大写的字符串
NSLog(@"string2:%@",[string2 lowercaseString]);//lowercaseString返回转换为小写的字符串
NSLog(@"string2:%@",[string2 capitalizedString]);//capitalizedString返回每个单词首字母大写的字符串

在串中搜索子串

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];

抽取子串

1、-substringToIndex: 从字符串的开头一直截取到指定的位置，但不包括该位置的字符

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringToIndex:3]; 
NSLog(@"string2:%@",string2);

2、-substringFromIndex: 以指定位置开始（包括指定位置的字符），并包括之后的全部字符

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringFromIndex:3];
NSLog(@"string2:%@",string2);

3、-substringWithRange: //按照所给出的位置，长度，任意地从字符串中截取子串

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
NSLog(@"string2:%@",string2);

4、快速枚举

for(NSString *filename in direnum)    {
    if([[filename pathExtension] isEqualToString:@"jpg"]){
        [files addObject:filename];
    }
}
NSLog(@"files:%@",files);

5、枚举

NSEnumerator *filenum;
filenum = [files objectEnumerator];
while (filename = [filenum nextObject]) {
    NSLog(@"filename:%@",filename);
}
@"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];

切分数组

1、从字符串分割到数组－ componentsSeparatedByString:

NSString *string = [[NSString alloc] initWithString:@"One,Two,Three,Four"];
NSLog(@"string:%@",string);   
NSArray *array = [string componentsSeparatedByString:@","];
NSLog(@"array:%@",array);
[string release];

2、从数组合并元素到字符串- componentsJoinedByString:

NSArray *array = [[NSArray alloc] initWithObjects:@"One",@"Two",@"Three",@"Four",nil];
NSString *string = [array componentsJoinedByString:@","];
NSLog(@"string:%@",string);

从目录搜索扩展名为jpg的文件

NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *home;
home = @"../Users/";
NSDirectoryEnumerator *direnum;
direnum = [fileManager enumeratorAtPath: home];
NSMutableArray *files = [[NSMutableArray alloc] init];

枚举

NSString *filename;
while (filename = [direnum nextObject]) {
    if([[filename pathExtension] hasSuffix:@"jpg"]){
        [files addObject:filename];
    }
}

扩展路径

NSString *Path = @"~/NSData.txt";
NSString *absolutePath = [Path stringByExpandingTildeInPath];
NSLog(@"absolutePath:%@",absolutePath);
NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);

文件扩展名

NSString *Path = @"~/NSData.txt";
NSLog(@"Extension:%@",[Path pathExtension]);

查找与替换

-(NSString *)stringByReplacingCharactersInRange:(NSRange)range withString:(NSString *)replacement
-(NSString *)stringByReplacingOccurrencesOfString:(NSString *)target withString:(NSString *)replacement

NSMutableString(可修改的字符串)

  NSObject -> NSString -> NSMutableString 
 Common NSMutableString methods
 +(id)string;
 -(void)appendString:(NSString *)string;
 -(void)appendFormat:(NSString *)format, ...;

给字符串分配容量

//stringWithCapacity:
NSMutableString *String;
String = [NSMutableString stringWithCapacity:40];

在已有字符串后面添加字符

//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);

在已有字符串中按照所给出范围删除字符

 //deleteCharactersInRange:
 NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
 [String1 deleteCharactersInRange:NSMakeRange(0, 5)]; //删除指定范围（location=0，length=5）的字符串
 NSLog(@"String1:%@",String1);

在已有字符串后面在所指定的位置中插入给出的字符串

//-insertString: atIndex:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 insertString:@"Hi! " atIndex:0];
NSLog(@"String1:%@",String1);
[String1 insertString:@"and StringEnd", atIndex:[String1 length]];//在可变字符串的最后插入

将已有的空符串换成其它的字符串

//-setString:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 setString:@"Hello Word!"];
NSLog(@"String1:%@",String1);

查找

NSRange subRange = [String1 rangeOfString:@"is a"];

// 如果没查找到，则（subRange.location == NSNotFound）为真。

按照所给出的范围替换的原有的字符

//-setString:
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];     // 用于NSMutableString
NSLog(@"String1:%@",String1);

在给定的范围内查找并替换

-(NSUInteger)replaceOccurrencesOfString:(NSString *)target withString:(NSString *)replacement options:(NSStringCompareOptions)opts range:(NSRange)searchRange

判断字符串内是否还包含别的字符串(前缀，后缀)

1、检查字符串是否以另一个字符串开头- (BOOL) hasPrefix: (NSString *) aString;

NSString *String1 = @"NSStringInformation.txt";
[String1 hasPrefix:@"NSString"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO");
[String1 hasSuffix:@".txt"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO");

2、查找字符串某处是否包含给定的字符串 - (NSRange) rangeOfString: (NSString *) aString，这一点前面在串中搜索子串用到过

NSRange subRange;
subRange = [string1 rangeOfString:@"string A"];  //查找字符串 string1中是否包含“string A”。返回NSRange类型。
if(subRange.location == NSNotFound)
NSLog(@"String not found ");
else  NSLog(@"string is at index %lu, length is %lu", subRange.location, subRange.length);

NSDate

NSCalendarDate

NSCalendarDate对象包含了日期和时间、时区以及一个带有格式的字符串，它从NSDate继承而来。
NSCalendarDate对象是immutable的，一旦被创建，无法修改其中的时间和日期，当然可以修改那个带格式的字符串和时区。

以下是常用方法：

+(id)calendarDate; //创建当前日期和时间以及默认格式的NSCalendarDate对象，时区为机器设置好的时区。

 +(id)dateWithYear:(int)year
month:(unsigned)month
  day:(unsigned)day 
 hour:(unsigned)hour
 minute:(unsigned)minute
 second:(unsigned)second 
 timeZone:(NSTimeZone  *)aTimeZone 

-(int)dayOfCommonEra;  //得到从公元1年算起，有多少天
-(int)dayOfMonth;          //返回是月的第几天（1-31）
-(int)dayOfWeek;          //返回是周的第几天 （0-6）
-(int)dayOfYear;          //返回是年的第几天（1-366）
-(int)hourOfDay;          // 返回是日的第几个小时（0-23）
-(void)setCalendarFormate:(NSString *)format

创建NSCalendarDate对象

NSCalendarDate *now;
now = [NSCalendarDate calendarDate];
NSTimeZone *pacific = [NSTimeZone timeZoneWithName:@"PST"];
NSCalendarDate *hotTime = [NSCalendarDate dateWithYear:2011 month:2 day:3 hour:14 minute:0 second:0 timeZone:pacific];

NSData

使用文件时，需要频繁地将数据读入一个临时存储区，它通常成为缓冲区。

NSData类提供了一种简单的方式，它用来设置缓冲区、将文件的内容读入缓冲区，或将缓冲区的内容写到一个文件。
对于32位应用程序，NSDATA缓存区最多可以存储2GB的数据。
我们既可定义不变缓冲区（NSData类），也可定义可变的缓冲区（NSMutableData类）。

下面代码展示了如何将文件的内容读入内存缓冲区，然后再将缓冲区的内容写入到另一个文件中。

NSData *fileData;
NSFileManager *fileManager = [[NSFileManager alloc]init];
fileData = [fileManager contentsAtPath:path];  
[fileManager createFileAtPath:path2 contents:fileData attributes:nil];   //采用默认的属性值

类型转换 NSData -> NSString：

NSString *strData = [[NSString alloc]initWithData:fileData encoding:NSASCIIStringEncoding];

类型转换 NSString -> NSData：

NSData *fileData2 = [strData dataUsingEncoding:NSUTF8StringEncoding];

NSMutableData...（待续。。。）