简述：Cocoa框架中的NSPredicate用于查询，原理和用法都类似于SQL中的where，作用相当于数据库的过滤取。
最常用到的函数
+ (NSPredicate *)predicateWithFormat:(NSString *)predicateFormat, ...;
1.比较运算符 > 、< 、== 、 >= 、<= 、 !=
例：@"number >= 99"
2.范围运算符：IN 、BETWEEN
例：@"number BETWEEN {1,5}" @"address IN {'shanghai','nanjing'}"3.字符串本身:SELF 例：@"SELF == 'APPLE'"4.字符串相关：BEGINSWITH、ENDSWITH、CONTAINS例：@"name CONTAIN[cd] 'ang'" //包含某个字符串 @"name BEGINSWITH[c] 'sh'" //以某个字符串开头 @"name ENDSWITH[d] 'ang'" //以某个字符串结束注:[c]不区分大小写 , [d]不区分发音符号即没有重音符号 , [cd]既不区分大小写，也不区分发音符号。5.通配符：LIKE例：@"name LIKE[cd] '*er*'" //*代表通配符,Like也接受[cd]. @"name LIKE[cd] '???er*'"
6.正则表达式：MATCHES
例：NSString *regex = @"^A.+e$"; //以A开头，e结尾 @"name MATCHES %@",regex
实际应用:对NSArray进行过滤
NSArray *array = [[NSArray alloc]initWithObjects:@"beijing",@"shanghai",@"guangzou",@"wuhan", nil]; NSString *string = @"ang"; NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF CONTAINS %@",string]; NSLog(@"%@",[array filteredArrayUsingPredicate:pred]);
实际应用:判断字符串首字母是否为字母
NSString *regex = @"[A-Za-z]+"; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex]; if ([predicate evaluateWithObject:aString]) { }
实际应用:字符串替换
NSError* error = NULL; NSRegularExpression* regex = [NSRegularExpression regularExpressionWithPattern:@"(encoding=\")[^\"]+(\")" options:0 error:&error]; NSString* sample = @""; NSLog(@"Start:%@",sample); NSString* result = [regex stringByReplacingMatchesInString:sample options:0 range:NSMakeRange(0, sample.length) withTemplate:@"$1utf-8$2"]; NSLog(@"Result:%@", result);
实际应用:截取字符串
//组装一个字符串，需要把里面的网址解析出来 NSString *urlString=@"1Q84 BOOK1 "; //NSRegularExpression类里面调用表达的方法需要传递一个NSError的参数。下面定义一个 NSError *error; //http+:[^\\s]* 这个表达式是检测一个网址的。(?<=title\>).*(?=中内文字的正则表达式 NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=title\\>).*(?=%@<-",result); } }
实际应用:判断手机号码，电话号码函数
// 正则判断手机号码地址格式- (BOOL)isMobileNumber:(NSString *)mobileNum{ /** * 手机号码 * 移动：134[0-8],135,136,137,138,139,150,151,157,158,159,182,187,188 * 联通：130,131,132,152,155,156,185,186 * 电信：133,1349,153,180,189 */ NSString * MOBILE = @"^1(3[0-9]|5[0-35-9]|8[025-9])\\d{8}$"; /** 10 * 中国移动：China Mobile 11 * 134[0-8],135,136,137,138,139,150,151,157,158,159,182,187,188 12 */ NSString * CM = @"^1(34[0-8]|(3[5-9]|5[017-9]|8[278])\\d)\\d{7}$"; /** 15 * 中国联通：China Unicom 16 * 130,131,132,152,155,156,185,186 17 */ NSString * CU = @"^1(3[0-2]|5[256]|8[56])\\d{8}$"; /** 20 * 中国电信：China Telecom 21 * 133,1349,153,180,189 22 */ NSString * CT = @"^1((33|53|8[09])[0-9]|349)\\d{7}$"; /** 25 * 大陆地区固话及小灵通 26 * 区号：010,020,021,022,023,024,025,027,028,029 27 * 号码：七位或八位 28 */ // NSString * PHS = @"^0(10|2[0-5789]|\\d{3})\\d{7,8}$"; NSPredicate *regextestmobile = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", MOBILE]; NSPredicate *regextestcm = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", CM]; NSPredicate *regextestcu = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", CU]; NSPredicate *regextestct = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", CT]; if (([regextestmobile evaluateWithObject:mobileNum] == YES) || ([regextestcm evaluateWithObject:mobileNum] == YES) || ([regextestct evaluateWithObject:mobileNum] == YES) || ([regextestcu evaluateWithObject:mobileNum] == YES)) { if([regextestcm evaluateWithObject:mobileNum] == YES) { NSLog(@"China Mobile"); } else if([regextestct evaluateWithObject:mobileNum] == YES) { NSLog(@"China Telecom"); } else if ([regextestcu evaluateWithObject:mobileNum] == YES) { NSLog(@"China Unicom"); } else { NSLog(@"Unknow"); } return YES; } else { return NO; }}
实际应用:邮箱验证、电话号码验证
//是否是有效的正则表达式+(BOOL)isValidateRegularExpression:(NSString *)strDestination byExpression:(NSString *)strExpression{ NSPredicate *predicate = [NSPredicatepredicateWithFormat:@"SELF MATCHES %@", strExpression]; return [predicate evaluateWithObject:strDestination];}//验证email+(BOOL)isValidateEmail:(NSString *)email { NSString *strRegex = @"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{1,5}"; BOOL rt = [CommonTools isValidateRegularExpression:email byExpression:strRegex]; return rt;}//验证电话号码+(BOOL)isValidateTelNumber:(NSString *)number { NSString *strRegex = @"[0-9]{1,20}"; BOOL rt = [CommonTools isValidateRegularExpression:number byExpression:strRegex]; return rt;}
实际应用:NSDate进行筛选
//日期在十天之内:NSDate *endDate = [[NSDate date] retain];NSTimeInterval timeInterval= [endDate timeIntervalSinceReferenceDate];timeInterval -=3600*24*10;NSDate *beginDate = [[NSDate dateWithTimeIntervalSinceReferenceDate:timeInterval] retain];//对coredata进行筛选(假设有fetchRequest)NSPredicate *predicate_date =[NSPredicate predicateWithFormat:@"date >= %@ AND date <= %@", beginDate,endDate]; [fetchRequest setPredicate:predicate_date];//释放retained的对象[endDate release];[beginDate release];