OC字符串基本使用

一.不可变字符串的方法

创建字符串

  NSString *str0 = [[NSString alloc]init];
  //简单创建字符传
  NSString *str1 = @"skdjfksjdklfs";
  //对象方法创建字符传
  NSString *str2 = [[NSString alloc]initWithString:str1];
  //通过C语言中字符串创建OC语言中字符串
  char strc[20] = "this is the test ";
  NSString *str3 = [[NSString alloc]initWithUTF8String:str];
  //通过类创建字符串
  NSString *str4 = [NSString stringWithString:str1];
  NSString *str5 = [NSString stringWithUTF8String:strc];
  NSString * str6 = [NSString stringWithFormat:@"%@",str1];

从本地文件获取字符串

---

NSString *path  = @"Users/File";
NSString *string = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:/*&error*/nil];

从网络中获取

  NSURL *url = [NSURL URLWithString:@"http://www.baidu.com"];
  NSString *string = [NSString stringWithContentsOfURL:url encoding:NSUTF8StringEncoding error:nil];

字符串拼接

 NSString  *str1  =  @"skjdhjkshfkdsss";
 NSString *str2 = [str1  stringByAppendingString :@"!"];

字符串长度

 NSString *str = @"ghjkl;ksjhdfsidhfs";
 unsigned long len = [str length];

取其中一个字符串

char c  = [str1 characterAtIndex: 2];

比较连个字符串大小

NSString *str1 = @"skjdhjkshfkdsss"; NSString *str2 = @"skjdhjkshfksdlfjsfdsss"; NSComparisonResult result = [str1 compare:str2];

  if (result == NSOrderedAscending) {

    NSLog(@"str1 < str2");

  } else if (result== NSOrderedDescending){
    NSLog(@"str1 > str2");

  }else{
    NSLog(@"str1 = str2");

  }

大小写转换

NSString *string = @"jsjsdjk  sdhfjksj  sjdf";
NSString *str = [string lowercaseString];
NSString *str = [string uppercaseString];
NSSting *str = [string capitalizedString];

查找字符串

NSRange range = [string  rangeOfString:@"jsdjk"];
if (range.location == NSNotFound){

 //没有找到

} else {

}
if(range.length == 0){

//没有找到 如果找到了 length 就是要查找字符串的长度

}
//从右往左查
NSRange rangeFront = [string rangOfString:@"sdk"option:NSBackwardsSearch];

//判断前后缀
Bool isS = [str hasSuffix];
Bool isP = [str hasPrefix];

//将字符串转成数字
int num = [@"123" intValue];

//提取字符串 确定起始位置
  NSString *str = [@"skjdo lskdl lsl" substringFromIndex:2];

//确定结束位置
   NSString *str = [string6 substringToIndex:5];

//确定其实下标和结束位置（长度）
  NSString *str = [@"dskj" substringWithRange:NSMakeRange(1, 2)];

二.可变字符串的方法

 //创建空字符串
  NSMutableString *muStr = [[NSMutableString alloc]init];

  //capacity 表示的是一个大致范围
  NSMutableString *str = [[NSMutableString alloc]initWithCapacity:10];

  //可变字符串不能用此种方法创建 如果使用了 就是不可变字符串
  NSString *string = @"sdjksd";

  //通过对象方法创建可变字符传
  NSMutableString *str1 = [[NSMutableString alloc]initWithString:@"yes"];
  NSMutableString *str3 = [[NSMutableString alloc] initWithFormat:@"%@",str];

  //通过类方法创建可变字符串
  NSMutableString *muStr21 = [NSMutableString stringWithString:@"sds"];
  NSMutableString *mutStr33 = [NSMutableString stringWithFormat:@"%@",string];

 //通过本地文件
  NSMutableString *mut223 = [NSMutableString stringWithContentsOfURL:@"/Users/01-字符串/File"  encoding:NSUTF8StringEncoding error:nil];

  //通过网络
    NSMutableString *mutStr9 = [NSMutableString stringWithContentsOfURL:[NSURL URLWithString:@"http://www.baidu.com"] encoding:NSUTF8StringEncoding error:nil];

可变字符串增 字符串

  NSMutableString *mut = [NSMutableString stringWithString:@"sjhdj sihfsdiu"];
  [mut1 appendString:@"sdkjf"];
  [mut1 appendFormat:@"dsfsds"];

  //在任意位置添加
  [mut1 insertString:@"sdfs" atIndex:2];

  //删除任意位置字符串
  NSMutableString mut = [NSMutableString stringWithString:@"sdkjfsdk"];
  [mut deleteCharactersInRange:NSMakeRange(8, 8)];

    //修改字符串
  NSMutableString *mut5 = [NSMutableString stringWithString:@"sd sjd skjdf"];

  //直接用后面的字符串替代现有的字符串
  [mut5 setString:@"sdkfsf"];

  //用存在的字符串替换选中位置的字符串
  [mut5 replaceCharactersInRange:NSMakeRange(2, 2) withString:@"sdsf"];

  //查
  NSMutableString *mut6 = [NSMutableString stringWithString:@"sun is a girl "];
  for (int i= 0; i< [mut6 length]; i++) {
    char s = [mut6 characterAtIndex:i];
  }

将字符串funnel与字符串also之间的字符串提取出来，不可以数

NSString *string = @"NSString primitive (funnel) methods. A minimal subclass of NSString just needs to implement these, although we also recommend";
NSRange range1 = [string rangeOfString:@"funnel"];
NSRange range2 = [string rangeOfString:@"also"];
NSRange range = NSMakeRange(range1.location + range1.length, range2.location - range1.location - range1.length);
NSString *subString = [string substringWithRange:range];
NSLog(@"*%@*", subString);