OC 数据类型之间的转换方法

NSNumber转NSString:

假设现有一NSNumber的变量A，要转换成NSString类型的B

方法如下：

NSNumberFormatter* numberFormatter = [[NSNumberFormatter alloc] init];

B = [numberFormatter stringFromNumber:A];

NSString和float 还有int之间的转换

NSString *tempA = @"123";

NSString *tempB = @"456";

1，字符转int

int intString = [newString intValue];

2，字符转float

float floatString = [newString floatValue];

3，字符串拼接

NSString *newString = [NSString stringWithFormat:@"%@%@",tempA,tempB];

4，int转字符

NSString *stringInt = [NSString stringWithFormat:@"%d",intString];

5，float转字符

NSString *stringFloat = [NSString stringWithFormat:@"%f",intString];

NSString *a = [[NSString alloc] initWithString : @"5, 10, 2, 0, 0, 0.01, 1, 0.05, 0, 0, 0"];

NSArray *bullteData = [a componentsSeparatedByString:@","];

for (int i = 0; i < [bullteData count]; i++) {

NSLog(@"%f",[[NSString stringWithFormat:@"%@",[bullteData objectAtIndex:i]] floatValue]);

}

将字符串存到数组中，在读取的时候转换成需要的类型。

说法二：

1. NSString转化为UNICODE String：
(NSString*)fname ＝ @“Test”;
char fnameStr[10];
memcpy(fnameStr, [fname cStringUsingEncoding:NSUnicodeStringEncoding], 2*([fname length]));

与strcpy相比，memcpy并不是遇到'\0'就结束，而是一定会拷贝完n个字节

2. NSString 转化为 char *
NSString * str＝ @“Test”;
const char * a =[str UTF8String];

3.char * 转化为 NSString

NSString *str=[NSString stringWithCString  encoding:NSUTF8StringEncoding];

4. char * 转化 NSData
方法一：
char * a = (char*)malloc(sizeof(byte)*16);
NSData *data = [NSData dataWithBytes: a   length:strlen(a)];
方法二：
转换为NSString： - (id)initWithUTF8String:(const char *)bytes
然后用NSString的 - (NSData *)dataUsingEncoding:(NSStringEncoding)encoding

5. NSData 转化 char *
NSData data ；
char* a=[data bytes];

6. NSData 转化 NSString;

NSData* data;

NSString* aStr= ［NSString alloc] initWithData:data   encoding:NSASCIIStringEncoding];

7. NSString 转化 NSData对象

NSData* xmlData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding];

NSString 转化 NSURL  

//NSURL *url = [NSURL URLWithString:[str   stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding ]];

NSString *urlString=[@"http://www.google.com/search?client=safari&rls=en&q=搜索&ie=UTF-8&oe=UTF-8" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSURL 转化 NSString

NSURL *url=[NSURL URLWithString:urlString];
NSString *s=[[url absoluteString] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSArray *arr = [urlStr componentsSeparatedByString:@"&"];
NSURL *url = [NSURL URLWithString:[[arr objectAtIndex:0] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding ]];
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
[request setHTTPMethod:@"POST"];

NSMutableArray *_array = [[NSMutableArray alloc] initWithCapacity:0];
for (int i = 1; i < [arr count]; ++i ){
NSString *str = [arr objectAtIndex:i];
[
　　_array addObject:str];
}
[_array componentsJoinedByString:@"&"];
NSData *data = [[_array componentsJoinedByString:@"&"] dataUsingEncoding: NSASCIIStringEncoding];
[request setHTTPBody:data];
// 发送请求并获得服务器反馈的数据
NSData *urldata = [AESEnCDeCViewController Get:url];

// 第一种 转换NSData数据到char*字符串
char * test = (char*)[urldata bytes];
std::string old = deaes(test);

// 第二种 转换NSData到UTF8编码的NSString中再转换为char*字符串
//  NSString *desStr = [[NSString alloc] initWithData:urldata encoding:NSUTF8StringEncoding];
//  const char *desresult = [desStr UTF8String];
//  std::string old = deaes(desresult);

// 解密字字符串到明文
NSString *oldstr = [[NSString alloc] initWithCString:old.c_str()];

很多时候软件读取的中文网页编码集是gb2312，所以显示出来的是乱码。这时需要将NSString文字编码转换

NSURL *url = [NSURL URLWithString:urlStr];
NSData *data = [NSData dataWithContentsOfURL:url];
NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);
NSString *retStr = [[NSString alloc] initWithData:data encoding:enc];