iOS Fundation-NSString & NSMutableString 使用详解

2015-02-03

iOS 使用过程中我们经常会使用到 Java 中类似字符串的函数和一些常量。在 iOS 中这些常量一般是以对象的形式存在。

NSString

（1）NSString 继承

1	NSString *name = @"bai liangliang";

在 Xcode 中按着 command + 鼠标左键，打开 NSString.h 的实现文档。可以看到下面代码：

@interface NSString : NSObject <NSCopying, NSMutableCopying, NSSecureCoding>

//省略...
...

@end

NSString 继承 NSObject 的对象，下面讲述 NSString 的相关使用方法。

（2）NSString 初始化

使用字符串直接初始化

1	NSString *name = @"bai liangliang";

使用类方法直接初始化

//使用现有的 string  字符对象直接进行初始化
+ (instancetype)string;
+ (instancetype)stringWithString:(NSString *)string;

//使用 字符来进行初始化
+ (instancetype)stringWithCharacters:(const unichar *)characters length:(NSUInteger)length;
+ (nullable instancetype)stringWithUTF8String:(const char *)nullTerminatedCString;

//使用 NSString 字符串来进行初始化
+ (instancetype)stringWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);
+ (instancetype)localizedStringWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);

//使用 字符来进行初始化 并且可以设置字符编码类型
+ (nullable instancetype)stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc;

//从 URL 或者 File 中获取字符串内容，并返回申请结果
+ (nullable instancetype)stringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;
+ (nullable instancetype)stringWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;
+ (nullable instancetype)stringWithContentsOfURL:(NSURL *)url usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;
+ (nullable instancetype)stringWithContentsOfFile:(NSString *)path usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;

使用上面的 API 进行 NSString 初始化的实例

1	NSString *nameString = [NSString stringWithString:name];

使用实例方法直接初始化

//直接初始化
- (instancetype)init NS_DESIGNATED_INITIALIZER;
- (nullable instancetype)initWithCoder:(NSCoder *)aDecoder

//使用 char 字符来进行字符串的初始化
- (instancetype)initWithCharactersNoCopy:(unichar *)characters length:(NSUInteger)length freeWhenDone:(BOOL)freeBuffer;	/* "NoCopy" is a hint */
- (instancetype)initWithCharacters:(const unichar *)characters length:(NSUInteger)length;
- (nullable instancetype)initWithUTF8String:(const char *)nullTerminatedCString;

//使用 string 类进行字符的初始化
- (instancetype)initWithString:(NSString *)aString;

//使用 string 类型来进行初始化
- (instancetype)initWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);
- (instancetype)initWithFormat:(NSString *)format arguments:(va_list)argList NS_FORMAT_FUNCTION(1,0);
- (instancetype)initWithFormat:(NSString *)format locale:(nullable id)locale, ... NS_FORMAT_FUNCTION(1,3);
- (instancetype)initWithFormat:(NSString *)format locale:(nullable id)locale arguments:(va_list)argList NS_FORMAT_FUNCTION(1,0);

//使用 data 数据类进行 string 初始化
- (nullable instancetype)initWithData:(NSData *)data encoding:(NSStringEncoding)encoding;

//使用 字符 bytes 类进行 string 初始化
- (nullable instancetype)initWithBytes:(const void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding;
- (nullable instancetype)initWithBytesNoCopy:(void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding freeWhenDone:(BOOL)freeBuffer;

//使用 char 类进行初始化，并且可以设置编码方式
- (nullable instancetype)initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding;

//从 URL 或者 File 中获取字符串内容，并返回申请结果
- (nullable instancetype)initWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;
- (nullable instancetype)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;
- (nullable instancetype)initWithContentsOfURL:(NSURL *)url usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;
- (nullable instancetype)initWithContentsOfFile:(NSString *)path usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;

1	NSString *nameString = [[NSString alloc] initWithString:name];

（3）NSString 基本使用方法

获取当前字符的长度&获取具体位置的字符

NSUInteger lengthString = nameString.length;
unichar charString = [nameString characterAtIndex:7];
    
NSLog(@"length : %lu, char : %c", (unsigned long)lengthString, charString);

//打印结果：
//Fundation-Demo[83962:6678701] length : 14, char : n

获取某段字符

1
2
3

- (NSString *)substringFromIndex:(NSUInteger)from;//从某个具体位置开始获取字符
- (NSString *)substringToIndex:(NSUInteger)to;//从第一个字符到指定位置字符
- (NSString *)substringWithRange:(NSRange)range;//获取某段范围内的字符

字符串的比较

//字符串进行比较可以设置比较的类型
- (NSComparisonResult)compare:(NSString *)string;
- (NSComparisonResult)compare:(NSString *)string options:(NSStringCompareOptions)mask;
- (NSComparisonResult)compare:(NSString *)string options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToCompare;
- (NSComparisonResult)compare:(NSString *)string options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToCompare locale:(nullable id)locale;
- (NSComparisonResult)caseInsensitiveCompare:(NSString *)string;
- (NSComparisonResult)localizedCompare:(NSString *)string;
- (NSComparisonResult)localizedCaseInsensitiveCompare:(NSString *)string;
- (NSComparisonResult)localizedStandardCompare:(NSString *)string API_AVAILABLE(macos(10.6), ios(4.0), watchos(2.0), tvos(9.0));

//两个字符完全相同
- (BOOL)isEqualToString:(NSString *)aString;

//根据当前给定 string 来获取当前字符的范围
- (NSRange)rangeOfString:(NSString *)searchString;
- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask;
- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch;
- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(nullable NSLocale *)locale API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet;
- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet options:(NSStringCompareOptions)mask;
- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch;

//从第一个字符串开始获取当前的范围
- (NSRange)rangeOfComposedCharacterSequenceAtIndex:(NSUInteger)index;
- (NSRange)rangeOfComposedCharacterSequencesForRange:(NSRange)range API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));

对当前字符串添加

1
2

- (NSString *)stringByAppendingString:(NSString *)aString;//对现有的字符串进行连接
- (NSString *)stringByAppendingFormat:(NSString *)format, ...//对现有的字符串进行多个值的赋值

对当前字符进行分割

1
2

- (NSArray<NSString *> *)componentsSeparatedByString:(NSString *)separator;
- (NSArray<NSString *> *)componentsSeparatedByCharactersInSet:(NSCharacterSet *)separator API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));

对字符替换

1
2
3

- (NSString *)stringByReplacingOccurrencesOfString:(NSString *)target withString:(NSString *)replacement options:(NSStringCompareOptions)options range:(NSRange)searchRange API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
- (NSString *)stringByReplacingOccurrencesOfString:(NSString *)target withString:(NSString *)replacement API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));
- (NSString *)stringByReplacingCharactersInRange:(NSRange)range withString:(NSString *)replacement API_AVAILABLE(macos(10.5), ios(2.0), watchos(2.0), tvos(9.0));

把字符保存在本地

1
2

- (BOOL)writeToURL:(NSURL *)url atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError **)error;
- (BOOL)writeToFile:(NSString *)path atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError **)error;

NSMutableString

NSMutableString 继承自 NSString

下面列出 NSMutableString 使用方法：

字符串的初始化

//实例方法对 可变字符 进行初始化
- (NSMutableString *)initWithCapacity:(NSUInteger)capacity;
//类方法对 可变字符 进行初始化
+ (NSMutableString *)stringWithCapacity:(NSUInteger)capacity;

对字符内容替换

1	- (void)replaceCharactersInRange:(NSRange)range withString:(NSString *)aString;//替换一定范围内的字符

对特定字符相关修改

- (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;//在特定位置 插入相关字符
- (void)deleteCharactersInRange:(NSRange)range;//删除一定范围内字符
- (void)appendString:(NSString *)aString;//附加字符
- (void)appendFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);//附加多个字符
- (void)setString:(NSString *)aString;//设置特定字符

//在特定位置替换字符
- (NSUInteger)replaceOccurrencesOfString:(NSString *)target withString:(NSString *)replacement options:(NSStringCompareOptions)options range:(NSRange)searchRange;

//特定范围字符顺讯改变
- (BOOL)applyTransform:(NSStringTransform)transform reverse:(BOOL)reverse range:(NSRange)range updatedRange:(nullable NSRangePointer)resultingRange API_AVAILABLE(macos(10.11), ios(9.0), watchos(2.0), tvos(9.0));

今天这里仅仅对 NSString 和 NSMutableString 进行简单的一些整理，列出 iOS 中一些给定的 API 展示其基本的使用方法。

如果有兴趣读者可以自己探索下相关方法。