版本修改记录
| 版本号 | 修改时间 |
|---|---|
| V1.0 | 2017.04.01 |
前言
前篇对NSString在API的框架中进行了整体的把握和了解，可以点击NSString简单细说（一）链接过去，但是在使用的时候还是要看细节，所以接下来几篇就会着眼于细节，重点讲述NSString的使用。感兴趣的可以看我上面几篇。
1. NSString简单细说（一）—— NSString整体架构
NSString的初始化
NSString的初始化方法一共有21个，下面就细说这些方法的使用。
一、+ (instancetype)string;方法
上代码
// 1. + (instancetype)string;
NSString *str = [NSString string];
NSLog(@"str----%@",str);
看结果
// An empty string.
2017-04-03 11:27:29.749 NSString你会用吗？[1563:49138] str----
结论：该方法返回的字符串返回的是空的字符串。
二、- (instancetype)init;方法
上代码
// 2. - (instancetype)init;
//An initialized NSString object that contains no characters. The returned object may be different from the original receiver.
NSString *str = [[NSString alloc] init];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 11:37:46.633 NSString你会用吗？[1708:57507] str----0x10a9a08b0----
结论：该方法返回的是空的字符串。
三、- (instancetype)initWithBytes:(const void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding;方法
上代码
/**
*3. - (instancetype)initWithBytes:(const void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding;
*
* @param bytes :A buffer of bytes interpreted in the encoding specified by encoding.
* @param length :The number of bytes to use from bytes.
* @param encoding :The character encoding applied to bytes
*
* @return :If the length of the byte string is greater than the specified length a nil value is returned.
*/
NSUInteger length = 4;
const void *bytes = "aabbccdd";
NSString *str = [[NSString alloc] initWithBytes:bytes length:length encoding:NSUTF8StringEncoding];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 20:33:37.401 NSString你会用吗？[3364:138958] str----0xa000000626261614----aabb
结论：可以看见length长度为4，当字符串长度大于length，则会截取的字符串；否则，则会输出全长度字符串。
四、- (instancetype)initWithBytesNoCopy:(void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding freeWhenDone:(BOOL)freeBuffer;方法
上代码
/**
*4.- (instancetype)initWithBytesNoCopy:(void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding freeWhenDone:(BOOL)freeBuffer;
*
* @param bytes :A buffer of bytes interpreted in the encoding specified by encoding.
* @param length :The number of bytes to use from bytes.
* @param encoding :The character encoding applied to bytes
* @param freeBuffer :If YES, the receiver releases the memory with free() when it no longer needs the data; if NO it won’t.
*
* @return :An initialized NSString object containing length bytes from bytes interpreted using the encoding encoding. The returned object may be different from the original receiver.
*/
NSUInteger length = 4;
void *a = "aassddd";
NSString *str = [[NSString alloc] initWithBytesNoCopy:a length:length encoding:NSUTF8StringEncoding freeWhenDone:NO];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 20:47:17.738 NSString你会用吗？[3550:150321] str----0xa000000737361614----aass
这里如果freeBuffer设置为YES，在不用就会释放。
NSString *str = [[NSString alloc] initWithBytesNoCopy:a length:length encoding:NSUTF8StringEncoding freeWhenDone:YES];
看结果
NSString你会用吗？(3593,0x104a063c0) malloc: *** error for object 0x100cc5df9: pointer being freed was not allocated
结论：可以看见freeBuffer设置为YES后被释放了，就crash了。
五、- (instancetype)initWithCharacters:(const unichar *)characters length:(NSUInteger)length;方法
上代码
/**
*5. - (instancetype)initWithCharacters:(const unichar *)characters length:(NSUInteger)length;
*
* @param characters :A C array of UTF-16 code units; the value must not be NULL.
* Important:Raises an exception if characters is NULL, even if length is 0.
* @param length :The number of characters to use from characters.
*
* @return :An initialized NSString object containing length characters taken from characters. The returned object may be different from the original receiver.
*/
NSUInteger length = 4;
const unichar *a = "zzzzzzzz";
NSString *str = [[NSString alloc] initWithCharacters:a length:length];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 21:39:40.830 NSString你会用吗？[4339:190158] str----0x6000000301a0----空空空空
结论：简单不多说了。
六、- (instancetype)initWithCharactersNoCopy:(unichar *)characters length:(NSUInteger)length freeWhenDone:(BOOL)freeBuffer;方法
看代码
/**
* 6. - (instancetype)initWithCharactersNoCopy:(unichar *)characters length:(NSUInteger)length freeWhenDone:(BOOL)freeBuffer;
*
* @param characters :A C array of UTF-16 code units.
* @param length :The number of characters to use from characters.
* @param freeBuffer :If YES, the receiver releases the memory with free() when it no longer needs the data; if NO it won’t.
*
* @return :An initialized NSString object that contains length characters from characters. The returned object may be different from the original receiver.
*/
NSUInteger length = 4;
unichar *a = "zzzzzzzzzzzzzzzz";
NSString *str = [[NSString alloc] initWithCharactersNoCopy:a length:length freeWhenDone:NO];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 22:07:36.654 NSString你会用吗？[4637:206036] str----0x60800002fb20----空空空空
结论：简单不多说了。
七、- (instancetype)initWithString:(NSString *)aString;方法
看代码
/**
* 7. - (instancetype)initWithString:(NSString *)aString;
*
* @param aString :The string from which to copy characters. This value must not be nil.
* Important:Raises an NSInvalidArgumentException if aString is nil.
*
* @return :An NSString object initialized by copying the characters from aString. The returned object may be different from the original receiver.
*/
NSUInteger length = 4;
NSString *a = @"zzzzzzzzzzzzzzzz";
NSString *str = [[NSString alloc] initWithString:a];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 22:21:22.655 NSString你会用吗？[4777:213816] str----0x10c20b088----zzzzzzzzzzzzzzzz
结论：同上。
八、- (instancetype)initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding;方法
看代码
/**
* 8. - (instancetype)initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding;
*
* @param nullTerminatedCString :A C array of characters. The array must end with a NULL character; intermediate NULL characters are not allowed.
* @param encoding :The encoding of nullTerminatedCString
*
* @return :An NSString object initialized using the characters from nullTerminatedCString. The returned object may be different from the original receiver
*/
NSUInteger length = 4;
const char *a = "azzzzzzzzzzzzzzb";
NSString *str = [[NSString alloc] initWithCString:a encoding:NSUTF8StringEncoding];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 23:28:23.072 NSString你会用吗？[5359:238906] str----0x6080002428b0----azzzzzzzzzzzzzzb
结论：同上。
九、- (instancetype)initWithUTF8String:(const char *)nullTerminatedCString;方法
/**
* 9.- (instancetype)initWithUTF8String:(const char *)nullTerminatedCString;
*
* @param nullTerminatedCString :A NULL-terminated C array of bytes in UTF-8 encoding. This value must not be NULL. Important :Raises an exception if bytes is NULL.
*
* @return :An NSString object initialized by copying the bytes from bytes. The returned object may be different from the original receiver.
*/
const char *a = "azzzzzzzzzzzzzzb";
NSString *str = [[NSString alloc] initWithUTF8String:a];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 23:37:19.728 NSString你会用吗？[5466:246577] str----0x60000005de50----azzzzzzzzzzzzzzb
结论：同上。
十、- (instancetype)initWithFormat:(NSString *)format, ...;方法
/**
* 10.- (instancetype)initWithFormat:(NSString *)format, ...;
*
* @param format :A format string.This value must not be nil.
Important ：Raises an NSInvalidArgumentException if format is nil.
* @param ... :A comma-separated list of arguments to substitute into format.
Important： When working with text that’s presented to the user, use the localizedStringWithFormat: method, or the initWithFormat:locale: or initWithFormat:locale:arguments: method, passing currentLocale as the locale.
*
* @return :An NSString object initialized by using format as a template into which the remaining argument values are substituted according to the system locale. The returned object may be different from the original receiver.
*/
NSString *str = [NSString stringWithFormat:@"AAA"];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-03 23:46:49.096 NSString你会用吗？[5567:253709] str----0xa000000004141413----AAA
结论：简单不解释。
十一、- (instancetype)initWithFormat:(NSString *)format arguments:(va_list)argList;方法
上代码
/**
* 11.- (instancetype)initWithFormat:(NSString *)format arguments:(va_list)argList;
*
* @param format :A format string.This value must not be nil.
Important ：Raises an NSInvalidArgumentException if format is nil.
* @param argList :A list of arguments to substitute into format.
Important： When working with text that’s presented to the user, use the localizedStringWithFormat: method, or the initWithFormat:locale: or initWithFormat:locale:arguments: method, passing currentLocale as the locale.
*
* @return :An NSString object initialized by using format as a template into which the values in argList are substituted according to the current locale. The returned object may be different from the original receiver.
*/
[self list:@"AAA",@"BBB",@"CCC",nil];
- (void)list:(NSString *)string,...{
va_list argsList;
va_start(argsList, string);
if (string) {
//输出第一个字符串
NSLog(@"%@",string);
NSString *otherString;
while (1) {
//依次取得所有参数
otherString = va_arg(argsList, NSString*);
if (otherString == nil) {
break;
}
else {
otherString = [[NSString alloc] initWithFormat:otherString arguments:argsList];
NSLog(@"otherString---%@",otherString);
}
}
}
va_end(argsList);
}
看结果
2017-04-05 23:35:11.651 NSString你会用吗？[1648:49185] AAA
2017-04-05 23:35:11.651 NSString你会用吗？[1648:49185] otherString---BBB
2017-04-05 23:35:11.652 NSString你会用吗？[1648:49185] otherString---CCC
结论：直接读代码吧。
十二、- (instancetype)initWithFormat:(NSString *)format locale:(id)locale, ...;方法
看代码
/**
* 12.- (instancetype)initWithFormat:(NSString *)format locale:(id)locale, ...;
*
* @param format :A format string.This value must not be nil.
Important ：Raises an NSInvalidArgumentException if format is nil.
* @param locale An NSLocale object specifying the locale to use. To use the current locale, pass [NSLocale currentLocale]. To use the system locale, pass nil.For legacy support, this may be an instance of NSDictionary containing locale information.
* @param ... :A comma-separated list of arguments to substitute into format.
*
* @return :Returns an NSString object initialized by using a given format string as a template into which the remaining argument values are substituted according to given locale.
*/
NSString *str = [[NSString alloc] initWithFormat:@"AAA" locale:nil];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 16:31:19.671 NSString你会用吗？[3788:157995] str----0xa000000004141413----AAA
结论：简单不解释。
十三、- (instancetype)initWithFormat:(NSString *)format locale:(id)locale arguments:(va_list)argList;方法
上代码
/**
* 13.- (instancetype)initWithFormat:(NSString *)format locale:(id)locale arguments:(va_list)argList;
*
* @param format :A format string.This value must not be nil.
Important ：Raises an NSInvalidArgumentException if format is nil.
* @param locale An NSLocale object specifying the locale to use. To use the current locale, pass [NSLocale currentLocale]. To use the system locale, pass nil.For legacy support, this may be an instance of NSDictionary containing locale information.
* @param argList :A list of arguments to substitute into format.
*
* @return :An NSString object initialized by using format as a template into which values in argList are substituted according the locale information in locale. The returned object may be different from the original receiver.
*/
[self list:@"AAA",@"BBB",@"CCC",nil];
- (void)list:(NSString *)string,...{
va_list argsList;
va_start(argsList, string);
if (string) {
//输出第一个字符串
NSLog(@"%@",string);
NSString *otherString;
while (1) {
//依次取得所有参数
otherString = va_arg(argsList, NSString*);
if (otherString == nil) {
break;
}
else {
otherString = [[NSString alloc] initWithFormat:otherString locale:nil arguments:argsList];
NSLog(@"otherString---%@",otherString);
}
}
}
va_end(argsList);
}
看结果
2017-04-05 23:43:26.918 NSString你会用吗？[1770:55214] AAA
2017-04-05 23:43:26.919 NSString你会用吗？[1770:55214] otherString---BBB
2017-04-05 23:43:26.919 NSString你会用吗？[1770:55214] otherString---CCC
结论：直接看代码吧。
十四、- (instancetype)initWithData:(NSData *)data encoding:(NSStringEncoding)encoding;方法
上代码
/**
* 14.- (instancetype)initWithData:(NSData *)data encoding:(NSStringEncoding)encoding;
*
* @param data : An NSData object containing bytes in encoding and the default plain text format (that is, pure content with no attributes or other markups) for that encoding.
* @param encoding: The encoding used by data. For possible values, see NSStringEncoding.
*
* @return :Returns an NSString object initialized by converting given data into UTF-16 code units using a given encoding.
*/
const void *dataStr = "AAABBBCCC";
NSData *data = [NSData dataWithBytes:dataStr length:6];
NSString *str = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 18:01:04.676 NSString你会用吗？[4570:196034] str----0xa004242424141416----AAABBB
结论：简单不解释。
十五、+ (instancetype)stringWithFormat:(NSString *)format, ...;方法
上代码
/**
* 15. + (instancetype)stringWithFormat:(NSString *)format, ...;
*
* @param format : A format string.This value must not be nil.
Important ：Raises an NSInvalidArgumentException if format is nil.
* @param ...: A comma-separated list of arguments to substitute into format.
*
* @return :Returns a string created by using a given format string as a template into which the remaining argument values are substituted.
*/
NSString *str = [NSString stringWithFormat:@"a=%@,b=%@",@"AAA",@"BBB"];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 18:25:16.133 NSString你会用吗？[4762:205925] str----0x60800022a600----a=AAA,b=BBB
结论：简单不解释。
十六、+ (instancetype)localizedStringWithFormat:(NSString *)format, ...;方法
上代码
/**
* 16. + (instancetype)localizedStringWithFormat:(NSString *)format, ...;
*
* @param format : A format string.This value must not be nil.
Important ：Raises an NSInvalidArgumentException if format is nil.
* @param ...: A comma-separated list of arguments to substitute into format.
*
* @return :A string created by using format as a template into which the following argument values are substituted according to the formatting information in the current locale.
*/
NSString *str = [NSString localizedStringWithFormat:@"a=%@,b=%@",@"AAA",@"BBB"];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 18:34:00.899 NSString你会用吗？[4906:212813] str----0x600000030b80----a=AAA,b=BBB
结论：简单不解释。
十七、+ (NSString *)localizedUserNotificationStringForKey:(NSString *)key arguments:(NSArray *)arguments;方法
看代码
/**
* 17. + (NSString *)localizedUserNotificationStringForKey:(NSString *)key arguments:(NSArray *)arguments
*
* @param key : The key to use when looking up the string in the app’s Localizable.strings file.
* @param arguments: An array of values to substitute for escaped characters in the string.
*
* @return :Returns a localized string intended for display in a notification alert.
*/
我找到一段这样的代码
UNMutableNotificationContent* content = [[UNMutableNotificationContent alloc] init];
content.title = [NSString localizedUserNotificationStringForKey:@"Hello 5 seconds!" arguments:nil];
content.body = [NSString localizedUserNotificationStringForKey:@"Hello_message_body" arguments:nil];
content.subtitle = [NSString localizedUserNotificationStringForKey:@"good day" arguments:nil];
content.sound = [UNNotificationSound defaultSound];
注意这里key为 in the app’s Localizable.strings file。arguments可以传nil。
结论：这里要注意Localizable.strings file。
十八、+ (instancetype)stringWithCharacters:(const unichar *)characters length:(NSUInteger)length;方法
上代码
/**
* 18. + (instancetype)stringWithCharacters:(const unichar *)characters length:(NSUInteger)length;
*
* @param characters : A C array of UTF-16 code units; the value must not be NULL. Important: Raises an exception if chars is NULL, even if length is 0.
* @param length:The number of characters to use from chars.
*
* @return :Returns a string containing a given number of characters taken from a given C array of UTF-16 code units.
*/
const unichar *charStr = "zzzzzzzzzzzzzzzz";
NSString *str = [NSString stringWithCharacters:charStr length:4];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 21:31:13.120 NSString你会用吗？[5835:261446] str----0x600000025840----空空空空
结论：简单不叙。
十九、+ (instancetype)stringWithString:(NSString *)string;方法
上代码
/**
* 19. + (instancetype)stringWithString:(NSString *)string;
*
* @param string : The string from which to copy characters. This value must not be nil. Important: Raises an NSInvalidArgumentException if aString is nil.
*
* @return :Returns a string created by copying the characters from another given string.
*/
NSString *string = @"AABBCCDD";
NSString *str = [NSString stringWithString:string];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 21:35:30.768 NSString你会用吗？[5900:265086] str----0x1084cf088----AABBCCDD
结论：简单不叙。
二十、+ (instancetype)stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc方法
上代码
/**
* 20. + (instancetype)stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc
*
* @param cString : A C array of bytes. The array must end with a NULL byte; intermediate NULL bytes are not allowed.
* @param enc : The encoding of cString.
*
* @return :Returns a string containing the bytes in a given C array, interpreted according to a given encoding.
*/
const char *cString = "AABBCCDD";
NSString *str = [NSString stringWithCString:cString encoding:NSUTF8StringEncoding];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 21:50:33.245 NSString你会用吗？[6091:275251] str----0xa00cb2bef6db8618----AABBCCDD
结论：简单不叙。
二十一、+ (instancetype)stringWithUTF8String:(const char *)nullTerminatedCString;方法
上代码
/**
* 21. + (instancetype)stringWithUTF8String:(const char *)nullTerminatedCString;
*
* @param nullTerminatedCString : A NULL-terminated C array of bytes in UTF8 encoding. Important： Raises an exception if bytes is NULL.
*
* @return :Returns a string created by copying the data from a given C array of UTF8-encoded bytes.
*/
const char *cString = "AABBCCDD";
NSString *str = [NSString stringWithUTF8String:cString];
NSLog(@"str----%p----%@",str,str);
看结果
2017-04-04 22:01:30.234 NSString你会用吗？[6258:283006] str----0xa00cb2bef6db8618----AABBCCDD
结论：简单不叙。
致谢
谢谢大家对我的关注，未完，待续~~~，我是刀客传奇，我是一个小码农。
