OC 自带方法 简绍 1 NSString

1.  initWithFormat   :  初始化一个 NString 类型

- (instancetype)initWithString:(NSString *)aString // Returns an NSString object initialized by copying the characters from another given string.

例子:

int n = 17;
NSString * s = [[NSString alloc] initWithFormat:@"蓝欧%d班", n];

2. length  : 得到NSString的长度

@property(readonly) NSUInteger length // The number of Unicode characters in the receiver. (read-only)

例子:

        NSString * str = @"河南17班";
        NSUInteger len = [str length];
        NSLog(@"长度是 %ld", len);

3. stringByAppendingString  :字符串拼接

- (NSString *)stringByAppendingString:(NSString *)aString //Returns a new string made by appending a given string to the receiver.

例子:

        NSString * str = @"蓝鸥";
        NSString * str2 = @"科技";
        NSString * str3 = [str stringByAppendingString:str2];
        NSLog(@"%@", str3);
4. stringByAppendingFormat   :  字符串拼接 带参数
- (NSString *)stringByAppendingFormat:(NSString *)format , ... // Returns a string made by appending to the receiver a string constructed from a given format string and the following arguments.

例子:

        int n =17;
        NSString * str =@"蓝鸥";
        NSString * newstr = [str stringByAppendingFormat:@"%d班", n];
        NSLog(@"%@", newstr);

5. substringFromIndex   : 得到某个字符从某个位数开始到结束

- (NSString *)substringFromIndex:(NSUInteger)anIndex //Returns a new string containing the characters of the receiver from the one at a given index to the end.

例子:

        NSString * str = @"蓝鸥科技";
        NSString * getString = [str substringFromIndex:2];
        NSLog(@"%@", getString);

6. substringToIndex  : 得到某段字符串从开始到某个位数结束

- (NSString *)substringToIndex:(NSUInteger)anIndex //Returns a new string containing the characters of the receiver up to, but not including, the one at a given index.

例子:

        NSString * str = @"蓝鸥科技";
        NSString * getString = [str substringToIndex:2];
        NSLog(@"%@", getString);

7.substringWithRange : 得到某段字符串从给定的范围

- (NSString *)substringWithRange:(NSRange)aRange //Returns a string object containing the characters of the receiver that lie within a given range.

例子1 :

        NSString * str = @"蓝鸥科技";
        NSRange range = {1, 2}; //或 NSRange range = NSMakeRange(1, 2);
        NSString * getString = [str substringWithRange:range];

例子2:

        NSString * str = @"蓝鸥科技";

        NSString * getString = [str substringWithRange:NSMakeRange(1, 2)];

        NSLog(@"%@", getString);

8. componentsSeparatedByString   字符串分割  

- (NSArray *)componentsSeparatedByString:(NSString *)separator // Returns an array containing substrings from the receiver that have been divided by a given separator.

例子:

        NSString * str = @"www.baidu.com";
        NSArray * subString = [str componentsSeparatedByString:@"."];
        NSLog(@"%@", subString);

9. rangeOfString          求子串 在原字符串中的范围

- (NSRange)rangeOfString:(NSString *)aString // Finds and returns the range of the first occurrence of a given string within the receiver.

例子:

        NSString * str = @"www.baidu.com";
        NSRange s = [str rangeOfString:@"bai"];
        NSLog(@"%lu %lu", s.location, s.length);

10.stringByReplacingOccurrencesOfString     替换元字符串中的字符  所有出现的某字符都替换成新字符

- (NSString *)stringByReplacingOccurrencesOfString:(NSString *)target
                                        withString:(NSString *)replacement 

// Returns a new string in which all occurrences of a target string in the receiver are replaced by another given string.

例子:

        NSString * str = @"你是我的小呀小苹果";
        NSString * s = [str stringByReplacingOccurrencesOfString:@"小" withString:@"大"];
        NSLog(@"%@", s);

11.hasPrefix   判断员字符串是不是以 某字符串打头 返回Bool

- (BOOL)hasPrefix:(NSString *)aString // Returns a Boolean value that indicates whether a given string matches the beginning characters of the receiver.

例子:

        NSString * str = @"http://www.baidu.com";
        BOOL b = [str hasPrefix:@"http://"];
        NSLog(@"%@", b ? @"YES" : @"NO");

12.hasSuffix  判断员字符串是不是以 某字符串结尾 返回Bool

- (BOOL)hasSuffix:(NSString *)aString //Returns a Boolean value that indicates whether a given string matches the ending characters of the receiver.

例子:

        BOOL b1 = [str hasSuffix:@".com"];
        NSLog(@"%@", b1 ? @"YES" : @"NO");

13.isEqualToString:  判断两个字符串是否相等

- (BOOL)isEqualToString:(NSString *)aString //Returns a Boolean value that indicates whether a given string is equal to the receiver using a literal Unicode-based comparison.

例子:

        NSString * str1 = @"蓝鸥科技";
        NSString * str2 = @"蓝鸥科技";
        BOOL b = [str1 isEqualToString:str2];
        NSLog(@"%@", b ? @"YES" : @"NO");

14.lowercaseString   大写转小写

@property(readonly, copy) NSString *lowercaseString     //   A lowercase representation of the string.

例子

        NSString * str1 = @"哈哈哈 hJJJkhjkJJJJ";
        NSString * s = [str1 lowercaseString];
        NSLog(@"%@", s);

15.uppercaseString   小写转大写

@property(readonly, copy) NSString *uppercaseString   //  An uppercase representation of the string. (read-only)

        NSString * str1 = @"hJJJkhjkJJJJ";

        NSString * s1 = [str1 uppercaseString];
        NSLog(@"%@", s1);

16.capitalizedString   单词首字母大写

@property(readonly, copy) NSString *capitalizedString   //  A capitalized representation of the receiver. (read-only)

        NSString * str = @"wo de xiao, yv ni xingle.";
        NSString * s3 = [str capitalizedString];
        NSLog(@"%@", s3);

17.integerValue  floatValue  doubleValue intvalue longlongValue boolValue字符串强制转换 函数

        NSString * a = @"861.1";
        NSString * b = @"657";
        NSInteger num = [a integerValue] + [b integerValue];
        NSLog(@"%ld", num);
        CGFloat num1 = [a floatValue] + [b floatValue];
        NSLog(@"%g", num1);