iOS NSString相关问题

1.NSString对象的创建

// 1.创建不可变字符串

NSString *str1 = @"create string";

#pragma mark 对象方法创建字符串

// 2.用另一个字符串初始当前字符串，指针所指地址相同

NSString *str2 = [[NSString alloc] initWithString:str1];

// 3.将其他的数据类型转化为字符串类型

NSString *str3 = [[NSString alloc] initWithFormat:@"Age is %d, Name is %@", 24, @"nick"];

#pragma mark 类方法创建字符串

// 4.该方法与initWithString方法对应

NSString *str4 = [NSString stringWithString:str1];

// 5.该方法与initWithFormat方法对应

NSString *str5 = [NSString stringWithFormat:@"Age is %d, Name is %@", 24, @"nick"];

NSLog(@"log-str1=%@-str2=%@-str3=%@-str4=%@-str5=%@",str1,str2,str3,str4,str5);

2.字符串的拼接

NSString *string1 = @"shang";

NSString *string2 = @"hai";

//- (NSString *)stringByAppendingString:(NSString *)aString;

//作用：将两个字符串进行拼接

//两个拼接的字符串都没有变，返回值是拼接后的字符串

NSString *string3 = [string1 stringByAppendingString:string2];

NSString *string4 = [NSString stringWithFormat:@"%@%@", string1, string2];

3.计算字符串的长度

　　NSString *string = @"shang-hai nice";

NSUInteger lenth = [string length];

NSLog(@"%zd",lenth);

4.取出字符串中对应位置的引用

　　NSString *string = @"zhou dong yu";

NSUInteger position = 1;

char character = [string characterAtIndex:position];

NSLog(@"%c",character);

5.在字符串中查找子串的位置

　　NSString *string1 = @"shang hai dong fang ming zhu";

NSString *string2 = @"ming";

//- (NSRange)rangeOfString:(NSString *)aString;

//作用：在一个字符串中查找子串的位置

//typedef struct _NSRange {

//    NSUInteger location;  起始位置

//    NSUInteger length;    从起始位置开始的长度

//} NSRange;

NSRange range = [string1 rangeOfString:string2];

if (range.location == NSNotFound) {

NSLog(@"没有找到");

}

NSLog(@"location is %lu, length is %lu", range.location, range.length);

6.字符串的比较

NSString *string1 = @"chen chao";

NSString *string2 = @"CHAN CHAO";

#if 0

//- (BOOL)isEqualToString:(NSString *)aString;

//作用：比较两个字符串是否完全相同

//BOOL：YES(真), NO(假)

BOOL bl = [string1 isEqualToString:string2];

if (bl) {

NSLog(@"string1 == string2");

} else{

NSLog(@"string1 != string2");

}

#endif

#if 0

//- (NSComparisonResult)compare:(NSNumber *)decimalNumber;

//作用：比较两个字符串是否相同(不忽略大小写)

//NSComparisonResult:NSOrderedAscending(升序)

//                   NSOrderedSame(相同)

//                   NSOrderedDescending(降序)

NSComparisonResult result = [string1 compare:string2];

if (result == NSOrderedDescending) {

NSLog(@"string1 < string2");

} else if (result == NSOrderedAscending) {

NSLog(@"string1 > string2");

} else {

NSLog(@"string1 == string2");

}

#endif

//- (NSComparisonResult)caseInsensitiveCompare:(NSString *)string;

//作用：比较两个字符串是否相同(忽略大小写)

NSComparisonResult result = [string1 caseInsensitiveCompare:string2];

if (result == NSOrderedDescending) {

NSLog(@"string1 < string2");

} else if (result == NSOrderedAscending) {

NSLog(@"string1 > string2");

} else {

NSLog(@"string1 == string2");

}