在实际项目开发过程中，发现字符串使用频率还是非常高的，NSString提供了很多相关的API，但是在开发过程中发现很多业务功能都是相同的。因此根据在开发过程中遇到的字符串使用场景，进行了简单封装。具体代码如下：

NSString+Category.h 代码:

//
// NSString+Category.h
// myApplication
//
// Created by xujinzhong on 2018/3/13.
// Copyright © 2018年 xujinzhong. All rights reserved.
//

#import

@interface NSString (Category)

• (BOOL)isBlank;

• (BOOL)isValid;

• (NSString *)removeWhiteSpacesFromString;

• (NSUInteger)countNumberOfWords;

• (BOOL)containsString:(NSString *)subString;

• (BOOL)isBeginsWith:(NSString *)string;

• (BOOL)isEndssWith:(NSString *)string;

• (NSString *)replaceCharcter:(NSString *)olderChar withCharcter:(NSString *)newerChar;

• (NSString*)getSubstringFrom:(NSInteger)begin to:(NSInteger)end;

• (NSString *)addString:(NSString *)string;

• (NSString *)removeSubString:(NSString *)subString;

• (BOOL)containsOnlyLetters;

• (BOOL)containsOnlyNumbers;

• (BOOL)containsOnlyNumbersAndLetters;

• (BOOL)isInThisarray:(NSArray*)array;

• (NSString *)getStringFromArray:(NSArray *)array;

• (NSArray *)getArray;

• (NSString *)getMyApplicationVersion;

• (NSString *)getMyApplicationName;

• (NSData *)convertToData;

• (NSString *)getStringFromData:(NSData *)data;

• (BOOL)isValidEmail;

• (BOOL)isVAlidPhoneNumber;

• (BOOL)isValidUrl;

@end

NSString+Category.m 代码:

//
// NSString+Category.m
// myApplication
//
// Created by xujinzhong on 2018/3/13.
// Copyright © 2018年 xujinzhong. All rights reserved.
//

#import "NSString+Category.h"

@implementation NSString (Category)

//字符串是否为空
-(BOOL)isBlank
{
return ([[self removeWhiteSpacesFromString] isEqualToString:@""]) ? YES : NO;
}

//字符串为空或nil
-(BOOL)isValid
{
return ([[self removeWhiteSpacesFromString] isEqualToString:@""] || self == nil || [self isEqualToString:@"(null)"]) ? NO :YES;
}

//在字符串中删除空格

• (NSString *)removeWhiteSpacesFromString
  {
  NSString *trimmedString = [self stringByTrimmingCharactersInSet:
  [NSCharacterSet whitespaceAndNewlineCharacterSet]];
  return trimmedString;
  }

//字符串中包含单词数

• (NSUInteger)countNumberOfWords
  {
  NSScanner *scanner = [NSScanner scannerWithString:self];
  NSCharacterSet *whiteSpace = [NSCharacterSet whitespaceAndNewlineCharacterSet];

  NSUInteger count = ;
  while ([scanner scanUpToCharactersFromSet: whiteSpace intoString: nil]) {
  count++;
  }

  return count;
  }

// 字符串中是否包含子字符串

• (BOOL)containsString:(NSString *)subString
  {
  return ([self rangeOfString:subString].location == NSNotFound) ? NO : YES;
  }

// 字符串从给定的字符串开始

• (BOOL)isBeginsWith:(NSString *)string
  {
  return ([self hasPrefix:string]) ? YES : NO;
  }

// 字符串以给定的字符串结束

• (BOOL)isEndssWith:(NSString *)string
  {
  return ([self hasSuffix:string]) ? YES : NO;
  }

// 用新字符替换字符串中的特定字符

• (NSString *)replaceCharcter:(NSString *)olderChar withCharcter:(NSString *)newerChar
  {
  return [self stringByReplacingOccurrencesOfString:olderChar withString:newerChar];
  }

// 从特定的位置获取子字符串，以使其正确

• (NSString*)getSubstringFrom:(NSInteger)begin to:(NSInteger)end
  {
  NSRange r;
  r.location = begin;
  r.length = end - begin;
  return [self substringWithRange:r];
  }

// 将子字符串添加到主字符串

• (NSString *)addString:(NSString *)string
  {
  if(!string || string.length == )
  return self;

  return [self stringByAppendingString:string];
  }

// 从字符串中删除指定字符串
-(NSString *)removeSubString:(NSString *)subString
{
if ([self containsString:subString])
{
NSRange range = [self rangeOfString:subString];
return [self stringByReplacingCharactersInRange:range withString:@""];
}
return self;
}

// 字符串只包含字母

• (BOOL)containsOnlyLetters
  {
  NSCharacterSet *letterCharacterset = [[NSCharacterSet letterCharacterSet] invertedSet];
  return ([self rangeOfCharacterFromSet:letterCharacterset].location == NSNotFound);
  }

// 字符串只包含数字

• (BOOL)containsOnlyNumbers
  {
  NSCharacterSet *numbersCharacterSet = [[NSCharacterSet characterSetWithCharactersInString:@""] invertedSet];
  return ([self rangeOfCharacterFromSet:numbersCharacterSet].location == NSNotFound);
  }

// 字符串中包含数字和字母

• (BOOL)containsOnlyNumbersAndLetters
  {
  NSCharacterSet *numAndLetterCharSet = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
  return ([self rangeOfCharacterFromSet:numAndLetterCharSet].location == NSNotFound);
  }

// 字符串包含在数组中

• (BOOL)isInThisarray:(NSArray*)array
  {
  for(NSString *string in array) {
  if([self isEqualToString:string]) {
  return YES;
  }
  }
  return NO;
  }

// 数组转换为字符串

• (NSString *)getStringFromArray:(NSArray *)array
  {
  return [array componentsJoinedByString:@" "];
  }

// 字符串转换为数组

• (NSArray *)getArray
  {
  return [self componentsSeparatedByString:@" "];
  }

// 获取应用程序版本

• (NSString *)getMyApplicationVersion
  {
  NSDictionary *info = [[NSBundle mainBundle] infoDictionary];
  NSString *version = [info objectForKey:@"CFBundleVersion"];
  return version;
  }

// 获取应用程序名称

• (NSString *)getMyApplicationName
  {
  NSDictionary *info = [[NSBundle mainBundle] infoDictionary];
  NSString *name = [info objectForKey:@"CFBundleDisplayName"];
  return name;
  }

// 字符串转换为NSData

• (NSData *)convertToData
  {
  return [self dataUsingEncoding:NSUTF8StringEncoding];
  }

// NSData转换为字符串

• (NSString *)getStringFromData:(NSData *)data
  {
  return [[NSString alloc] initWithData:data
  encoding:NSUTF8StringEncoding];
  }

// 是否为邮件格式

• (BOOL)isValidEmail
  {
  NSString *regex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}";
  NSPredicate *emailTestPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
  return [emailTestPredicate evaluateWithObject:self];
  }

// 是否为电话格式

• (BOOL)isVAlidPhoneNumber
  {
  NSString *regex = @"[235689][0-9]{6}([0-9]{3})?";
  NSPredicate *test = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
  return [test evaluateWithObject:self];
  }

// 是否为URL格式

• (BOOL)isValidUrl
  {
  NSString *regex =@"(http|https)://((\\w)*|([0-9]*)|([-|_])*)+([\\.|/]((\\w)*|([0-9]*)|([-|_])*))+";
  NSPredicate *urlTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@",regex];
  return [urlTest evaluateWithObject:self];
  }

@end