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([[s1

name]compare:
[s2name]] <0)
{
returnNSOrderedAscending;
}elseif([[s1

name]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);