NSString的API

NSString和NSMutableString的

 

//增加:

 

1、initWithFormat

原型: - (instancetype)initWithFormat:(NSString *)format

 

(1)  //用于给字符串初始化:

//例如

NSString* str = [[NSString alloc] initWithFormat:@"%@",@"Hello World”];

或者也可以这样写:

//例如

NSString* str = [[NSString alloc] initWithFormat:@"Hello World”];

 

(2)  //也可以用它来将数字转换成字符串.

//例如

NSString *str1 = [[NSString alloc] initWithFormat:@“%d”, 123];

 

(3) //也可以用于拼接:

//例如

NSString *str2 = [[NSString alloc] initWithFormat:@“%@%@”, @“abc”, @“def”];

 

2. stringByAppendingString

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

//在字符串尾部追加一个字符串:

 

//例如

[string stringByAppendingString:@“jpg”];

 

3. appendString

//原型: - (void)appendString:(NSString *)aString;

//在一个可变字符串后面追加一个字符串;

 

//例如:

NSMutableString *string1 = [[NSMutableString alloc] initWithFormat:@"%@", @“老王是个好邻居"];

 [string1 appendString:@", 难道不是吗?"];

    NSLog(@"%@", string1);

//返回结果:老王是个好邻居, 难道不是吗?

 

4. initWithCapacity

//原型:- (NSMutableString *)initWithCapacity:(NSUInteger)capacity;

//估计要装多少个字符(将来如果要超了,就按照给的数字再去申请这么多的空间)

//例如:

// NSMutableString *string2 = [[NSMutableString alloc] initWithCapacity:10];

 

//删除

 

1.  deleteCharactersinRange

//原型:

-(void)deleteCharactersInRange:(NSRange)range;

// 从一个字符串里删除另一个字符串:

 NSMutableString *string1 = [[NSMutableString alloc] initWithFormat:@"%@", @"老王是个好邻居"];

NSRange r2 = [string1 rangeOfString:@"个好"];

    [string1 deleteCharactersInRange:r2];

    NSLog(@"%@", string1);

 

//返回结果: 老王是邻居

 

//修改

1. stringByReplacingOccurrencesOfString

//原型:

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

//在一个字符串中,把目标字符串都替换成你要的字符串.

 

把字符串中所有的.png替换成.jpg:

//例如:

[stringstringByReplacingOccurrencesOfString:@".png" withString:@“.jpg”];

 

2. @property (readonly) int intValue;

//利用intValue方法.可以把字符串转换成整形

//例如:

NSString *string5 = [[NSString alloc] initWithFormat:@"%d", 123];

    int a = [string5 intValue];

    NSLog(@"%d", a);

//返回结果: 123

 

3. replaceCharactersInRange

//原型-(void)replaceCharactersInRange:(NSRange)range withString:(NSString *)aString;

 

//从某个位置开始替换某段长度的字符串:

NSMutableString *string1 = [[NSMutableString alloc] initWithFormat:@"%@", @"老王是个好邻居"];

    NSRange r = [string1 rangeOfString:@"是个"];

[string1 replaceCharactersInRange:r withString:@"真是一"];

    NSLog(@"%@", string1);

 

//返回结果:老王真是一好邻居

 

4. insertString: atIndex:

//原型:

- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;

//在某个位置插入一个字符串:

//例如:

NSMutableString *string1 = [[NSMutableString alloc] initWithFormat:@"%@", @“老王是个好邻居"];

NSRange r1 = [string1 rangeOfString:@"邻居"];

    [string1 insertString:@"色胆包天" atIndex:r1.location];

    NSLog(@"%@", string1);

//返回结果: 老王是个好色胆包天邻居

 

5. @property (readonly) float floatValue

//把字符串转换成float类型.

 NSString *stringnu = [[NSString alloc] initWithFormat:@"%f", 12.0544];

    NSLog(@"%@", stringnu);

    float c = stringnu.floatValue;

    NSLog(@"%.2f", c);

//返回结果: 12.05

 

6. componentsSeparatedByString

//原型-(NSArray*)componentsSeparatedByString:(NSString *)separator;

//把一个字符串按照某个字符串分成2个字符串数组:

//例如:

NSArray *array = [[NSArray alloc] initWithObjects:nil];

    NSString *str = [[NSString alloc] initWithFormat:@"abcdefg"];

    array = [str componentsSeparatedByString:@“de"];

 for (int i = 0; i < [array count]; i++) {

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

 }

//返回结果: abc

              fg

 

4. @property (readonly, copy) NSString *uppercaseString;

//把所有字母变成大写;

NSString *str = [[NSString alloc] initWithFormat:@"aBcdEfg"];

 NSLog(@"%@", [str uppercaseString]);

//返回结果: ABCDEFG

 

5. @property (readonly, copy) NSString *lowercaseString;

//把所有字母变成小写.

NSString *str = [[NSString alloc] initWithFormat:@“aBcdEfg"];

NSLog(@"%@", [str lowercaseString]);

//返回结果abcdefg

6. @property (readonly, copy) NSString *capitalizedString;

//除了首字母大写,剩下字母无论大小写,都是小写

NSString *str = [[NSString alloc] initWithFormat:@“aBcdEfg"];

 NSLog(@"%@", [str capitalizedString]);

 

//返回结果:Abcdefg

 

 

//查询

1. length

[str length]

//测试字符串长度

NSString *str3 = @“abcfdf.sdf”;

NSLog(@“%lu”, [str3 length]);//求字符串长度的方法.(小数点也算一位.)正确答案10(没有’\0’);

 

 

2. hasSuffix

//原型:

- (BOOL)hasSuffix:(NSString *)aString;

//查询以什么结尾!

NSString *string = [[NSString alloc] initWithFormat:@"%@", @“xxx.png"];

[string hasSuffix:@“png"]  如果用png结尾的话返回1

否则是0

 

3. hasPrefix

//原型:

- (BOOL)hasPrefix:(NSString *)aString;

查询以什么开头!

NSString *string = [[NSString alloc] initWithFormat:@"%@", @“xxx.png"];

[string hasPrefix:@“png"]  如果用png开头的话返回1

否则是0

 

 

 

 

 

4. substringFromIndex

//原型:

- (NSString *)substringFromIndex:(NSUInteger)from;

 

//从输入的数字开始截取(包括开始那位)字符串到结束:

//例如:NSString *string = [[NSString alloc] initWithFormat:@"%@", @"老王是个好邻居"];

NSString *s1 = [string substringFromIndex:3];

    NSLog(@"s1 = %@", s1);

//输出结果是:s1 = 个好邻居

 

 

5. substringToIndex

//原型-(NSString*)substringToIndex:(NSUInteger)to;

 

//从第一个字符往后截取几个字符:

NSString *string = [[NSString alloc] initWithFormat:@"%@", @“老王是个好邻居"];

 NSString *s2 = [string substringToIndex:3];

    NSLog(@"s2 = %@", s2);

//输出结果是:s2 = 老王是

 

 

6 substringWithRange

//原型:

-(NSString*)substringWithRange:(NSRange)range;

 

从某一个位置向后截取一段长度的字符串

NSString *string = [[NSString alloc] initWithFormat:@"%@", @"老王是个好邻居"];

NSRange ns = NSMakeRange(2, 3);

    NSString *s3 = [string substringWithRange:ns];

    NSLog(@"s3 = %@", s3);

//输出结果: 是个好

 

7. compare

//原型

- (NSComparisonResult)compare:(NSString *)string;

 

//比较2个字符串大小,如果左边大返回正1,否则-1,相等返回0

NSLog(@"%ld", [@"l" compare:@"z"]);

//返回 -1

 

8. caseInsensitiveCompare

//例如:

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

 

//比较2个字符串(忽略大小写)如果左边大返回正1,否则-1,相等返回0

NSLog(@"%ld", [@"z" caseInsensitiveCompare:@“Z"]);

//返回 0

 

9. isEqualToString:

//原型

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

 

//比较两个字符串是否相等, 相等返回1,否则0:

NSString *s4 = [[NSString alloc] initWithFormat:@"小王"];

    NSString *s5 = @"小王";

NSLog(@"%d", s4 == s5);

//比较的是s4和s5的指针的值.    NSLog(@"%d", [s4 isEqualToString:s5]);//比较的是他们对应地址里存得字符串

// 结果是 0  和  1

 

10. containsString

//例如:

- (BOOL)containsString:(NSString *)aString

//查看左边字符串里面包含不包含右面的字符串

NSString *s4 = [[NSString alloc] initWithFormat:@“abcde”];

if ([s4 containsString:@"b"]) {

        NSLog(@"yes");

    }

    else {

        NSLog(@"no");

    }

//返回结果   yes

 

11  rangeOfString

//原型:

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

//发送一个要查找的字符串.如果找到了,返回那个字符串的开始位置和长度:

NSString *string1 = [[NSString alloc] initWithFormat:@"老王是个好邻居"];

    NSString *string2 = @"是个";

    NSRange ns = [string1 rangeOfString:string2];

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

    NSLog(@"%@", NSStringFromRange(ns));

 

//返回结果 {2, 2};

 

 

12. characterAtIndex

//例如:

-(unichar)characterAtIndex:(NSUInteger)index;

//截取某一个位置上的字符.

NSString *string = [[NSString alloc] initWithFormat:@"%@", @“abcde"];

NSLog(@"%c", [string characterAtIndex:4]);

//返回结果: e