IOS开发常用代码汇总5

38. 对字符串的使用

1）、创建常量字符串。

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

 

   2）、创建空字符串，给予赋值。

   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 aString!"];

   NSLog(@"astring:%@",astring);

   [astring release];

 

   4）、用标准c创建字符串:initWithCString方法

   char *Cstring = "This is a String!";

   NSString *astring = [[NSString alloc] initWithCString:Cstring];

   NSLog(@"astring:%@",astring);

   [astring release];

 

   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:[NSStringstringWithFormat:@"%d.This is %i string!",i,j]];

   NSLog(@"astring:%@",astring);

   [astring release];

 

   6）、创建临时字符串

   NSString *astring;

   astring = [NSString stringWithCString:"This is a temporarystring"];

   NSLog(@"astring:%@",astring);

 

   /*----------------从文件读取字符串:initWithContentsOfFile方法 ----------------*/

   NSString *path = @"astring.text";

   NSString *astring = [[NSString alloc] initWithContentsOfFile:path];

   NSLog(@"astring:%@",astring);

   [astring release];

 

   /*----------------写字符串到文件:writeToFile方法 ----------------*/

   NSString *astring = [[NSString alloc] initWithString:@"This is aString!"];

   NSLog(@"astring:%@",astring);

   NSString *path = @"astring.text";

   [astring writeToFile: path atomically: YES];

   [astring release];   

 

   /*---------------- 比较两个字符串----------------*/

用C比较:strcmp函数

   char string1[] = "string!";

   char string2[] = "string!";

   if(strcmp(string1, string2) = = 0)

   {

       NSLog(@"1");

   }

 

   isEqualToString方法

   NSString *astring01 = @"This is a String!";

   NSString *astring02 = @"This is a String!";

   BOOL result = [astring01 isEqualToString:astring02];

   NSLog(@"result:%d",result);

 

   compare方法(comparer返回的三种值)

   NSString *astring01 = @"This is a String!";

   NSString *astring02 = @"This is a String!";

   BOOL result = [astring01 compare:astring02] = = NSOrderedSame;

   NSLog(@"result:%d",result);

   NSOrderedSame 判断两者内容是否相同

 

   NSString *astring01 = @"This is a String!";

   NSString *astring02 = @"this is a String!";

   BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;

   NSLog(@"result:%d",result);

   //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)

 

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)

 

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]);//大写

   NSLog(@"string2:%@",[string2 lowercaseString]);//小写

   NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小

 

   /*----------------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:[NSStringstringWithFormat:@"Location:%i,Leight:%i"

                        ,location,leight]];

   NSLog(@"astring:%@",astring);

   [astring release];

 

   /*----------------抽取子串 ----------------*/

   -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);

 

   -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);

 

   -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);

 

const char *fieldValue = [value  cStringUsingEncoding:NSUTF8StringEncoding];

const char *fieldValue = [valueUTF8String];

 

NSString 转 NSData

NSString* str= @"kilonet";

NSData* data=[strdataUsingEncoding:NSUTF8StringEncoding];

 

  Date format用法：

 -(NSString *) getDay:(NSDate *) d

{

   NSString *s ;

   NSDateFormatter *format = [[NSDateFormatter alloc] init];

   [format setDateFormat:@"YYYY/MM/dd hh:mm:ss"];

   s = [format stringFromDate:d];

   [format release];

   return s;

}

 

38. 判断设备

if([[UIDevice currentDevice] userInterfaceIdiom] == UIUserInterfaceIdiomPad) ｛

NSLog(@"ipad");

｝

else

{

NSLog(@"iphoneor ipod");

}

39.获取设备名称、设备类型、系统名称、系统版本

 UIDevice* device = [UIDevice currentDevice];
NSString* os = [device systemVersion];// 系统版本
NSString* systemModel = [device model];//设备类型
NSString* systemName = [device systemName ];// 系统名称
NSString* phoneName = [device name];//手机名称
    

 

40.获取上下文

CGContextRefcontext = UIGraphicsGetCurrentContext();

 

41.获得DemoAppDelegate

            DemoAppDelegate *appDelegate=[(DemoAppDelegate*)[UIApplication sharedApplication] ].delegate;