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");
}