OC之对不可变字符串、可变字符串、可变数组的操作及OC中字符串的排序

对不可变字符串的操作：

NSString*str = [[NSStringalloc]initWithString:@"^封枭^"];

NSLog(@"str = %@",str);

NSString*str1 = [NSStringstringWithString:@"-若雪-"];

NSLog(@"str1 = %@",str1);

//求字符串长度.length

 NSUIntegerlength  = str1.length;

 NSLog(@"lenth = %lu",length);

//字符串拼接

 NSString*str2 = [str1 stringByAppendingString:str];

 NSLog(@"str2 = %@",str2);

//多个字符串的拼接

NSString*str3 = [str stringByAppendingFormat:@"%@%@%@",str1,str,str2];

NSLog(@"str3 = %@",str3);

//字符串替换

NSString*str4 = [str stringByReplacingOccurrencesOfString:strwithString:str1];

NSLog(@"str4 = %@",str4);

//在（x，y）范围替换字符串

NSString*str5 = [str1 stringByReplacingCharactersInRange:NSMakeRange(1,3)withString:@"微笑"];

NSLog(@"str5 = %@",str5);

//字符串替换为@“xx”

NSString*str6 = [str stringByReplacingOccurrencesOfString:strwithString:@"后会无期"];

NSLog(@"str6 = %@",str6);

对可变字符串的操作：

NSMutableString*m = [[NSMutableStringalloc]initWithString:@"若你安好…"];

//拼接

[mappendString:@"便是晴天···"];

NSLog(@"%@",m);

//插入字符

[minsertString:@"微微一笑很倾城"atIndex:12];

NSLog(@"%@",m);

//删除字符串

[mdeleteCharactersInRange:NSMakeRange(0,1)];

NSLog(@"%@",m);

[mdeleteCharactersInRange:NSMakeRange(0,0)];

NSLog(@"%@",m);

NSString是不可改变字符串，创建出来后不能改变长度和内容

NSMutablleString是可变字符串，创建之后可以修改内容

可变(NSMutableString)和不可变(NSString)

不可变字符串的修改操作，本质是得到一个新的字符串。
不可变字符串的修改是以string开头，有返回值。

可变字符串的修改方法没有返回值，修改原字符串。

//不可变字符串的修改

NSString*result1 = @"y.png";

NSString*newresult = [NSStringstring];

if([result1hasSuffix:@"png"]) {

newresult = [result1stringByReplacingOccurrencesOfString:@"png"withString:@"jpg"];

}else{

newresult = [result1stringByAppendingString:@".jpg"];

}

NSLog(@"newresult = %@",newresult);

       

//可变字符串的修改

NSString*n = [[NSMutableStringalloc]initWithString:@"k.png"];

if([nhasSuffix:@"k.png"]) {

n = [nstringByReplacingOccurrencesOfString:@"png"withString:@"jpg"];

}else{

n = [nstringByAppendingString:@".jpg"];

}

NSLog(@"n = %@",n);

字符串排序：用compare比较

 if([[s1name]compare: [s2name]] <0) {

  returnNSOrderedAscending;

   }elseif([[s1name]compare: [s2name]] >0){

   returnNSOrderedDescending;

    }else{

  returnNSOrderedSame;

  }

对可变数组的操作

NSMutableArray*ma = [[NSMutableArrayalloc]initWithObjects:@"她说",@"阴天",@"明天，你好",@"离歌",nil];

[maaddObject:@""];

for(inti = 0; i < array.count; i++) {

NSLog(@"%@",array[i]);

}

//插入

[mainsertObject:@"日不落"atIndex:3];

//删除

[maremoveObjectAtIndex:3];

for(inti = 0; i < ma.count; i++) {

NSLog(@" 3%@",ma[i]);

}

//替换

[mareplaceObjectAtIndex:4withObject:@"天亮了"];

for(inti = 0; i < ma.count; i++) {

NSLog(@" 4%@",ma[i]);

}

//交换指定位置的元素

[maexchangeObjectAtIndex:2withObjectAtIndex:1];

for(inti = 0; i < ma.count; i++) {

NSLog(@" 5%@",ma[i]);

}

//把int类型转换为NSNumber对象类型存入数组

NSNumber*o1 = [NSNumbernumberWithInt:123];

NSNumber*o2 = [NSNumbernumberWithInt:234];

//把float转换为NSNumber对象存入数组

NSNumber*o3 = [NSNumbernumberWithFloat:'A'];

NSNumber*o4 = [NSNumbernumberWithFloat:'Y'];

//把数组元素取出来，用xxxValue在转换为原来类型

NSArray*a2 = [NSArrayarrayWithObjects:o1,o2,o3,o4,nil];

intw = [[a2 objectAtIndex:0]intValue];

NSLog(@"a2 = %d",w);

floatb = [[a2 objectAtIndex:3]intValue];

NSLog(@"a2 = %.fd",b);