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。
定义(最常用到的方法):
- NSPredicate*ca=[NSPredicatepredicateWithFormat:(NSString*),...];
Format:
(1)比较运算符>,<,==,>=,<=,!=
可用于数值及字符串
例:@"number > 100"
(2)范围运算符:IN、BETWEEN
例:@"number BETWEEN {1,5}"
@"address IN {'shanghai','beijing'}"
(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: (1)对NSArray进行过滤
- NSArray*array=[[NSArrayalloc]initWithObjects:@"beijing",@"shanghai",@"guangzou",@"wuhan",nil];
- NSString*string=@"ang";
- NSPredicate*pred=[NSPredicatepredicateWithFormat:@"SELFCONTAINS%@",string];
- NSLog(@"%@",[arrayfilteredArrayUsingPredicate:pred]);
(2)判断字符串首字母是否为字母:
- NSString*regex=@"[A-Za-z]+";
- NSPredicate*predicate=[NSPredicatepredicateWithFormat:@"SELFMATCHES%@",regex];
- if([predicateevaluateWithObject:aString]){
- }
(3)字符串替换:
- NSError*error=NULL;
- NSRegularExpression*regex=[NSRegularExpressionregularExpressionWithPattern:@"(encoding=")[^"]+(")"
- options:0
- error:&error];
- NSString*sample=@"<xmlencoding="abc"></xml><xmlencoding="def"></xml><xmlencoding="ttt"></xml>";
- NSLog(@"Start:%@",sample);
- NSString*result=[regexstringByReplacingMatchesInString:sample
- options:0
- range:NSMakeRange(0,sample.length)
- withTemplate:@"$1utf-8$2"];
- NSLog(@"Result:%@",result);
(4)截取字符串如下:
- NSString*urlString=@"<meta/><link/><title>1Q84BOOK1</title></head><body>";
- NSError*error;
- NSRegularExpression*regex=[NSRegularExpressionregularExpressionWithPattern:@"(?<=title>).*(?=</title)"options:0error:&error];
- if(regex!=nil){
- NSTextCheckingResult*firstMatch=[regexfirstMatchInString:urlStringoptions:0range:NSMakeRange(0,[urlStringlength])];
- if(firstMatch){
- NSRangeresultRange=[firstMatchrangeAtIndex:0];
- NSString*result=[urlStringsubstringWithRange:resultRange];
- NSLog(@"->%@<-",result);
- }
- }
(5)判断手机号码,电话号码函数
- -(BOOL)isMobileNumber:(NSString*)mobileNum
- {
- NSString*MOBILE=@"^1(3[0-9]|5[0-35-9]|8[025-9])d{8}$";
- NSString*CM=@"^1(34[0-8]|(3[5-9]|5[017-9]|8[278])d)d{7}$";
- NSString*CU=@"^1(3[0-2]|5[256]|8[56])d{8}$";
- NSString*CT=@"^1((33|53|8[09])[0-9]|349)d{7}$";
- NSPredicate*regextestmobile=[NSPredicatepredicateWithFormat:@"SELFMATCHES%@",MOBILE];
- NSPredicate*regextestcm=[NSPredicatepredicateWithFormat:@"SELFMATCHES%@",CM];
- NSPredicate*regextestcu=[NSPredicatepredicateWithFormat:@"SELFMATCHES%@",CU];
- NSPredicate*regextestct=[NSPredicatepredicateWithFormat:@"SELFMATCHES%@",CT];
- if(([regextestmobileevaluateWithObject:mobileNum]==YES)
- ||([regextestcmevaluateWithObject:mobileNum]==YES)
- ||([regextestctevaluateWithObject:mobileNum]==YES)
- ||([regextestcuevaluateWithObject:mobileNum]==YES))
- {
- if([regextestcmevaluateWithObject:mobileNum]==YES){
- NSLog(@"ChinaMobile");
- }elseif([regextestctevaluateWithObject:mobileNum]==YES){
- NSLog(@"ChinaTelecom");
- }elseif([regextestcuevaluateWithObject:mobileNum]==YES){
- NSLog(@"ChinaUnicom");
- }else{
- NSLog(@"Unknow");
- }
- returnYES;
- }
- else
- {
- returnNO;
- }
- }
(6)邮箱验证、电话号码验证:
- +(BOOL)isValidateRegularExpression:(NSString*)strDestinationbyExpression:(NSString*)strExpression
- {
- NSPredicate*predicate=[NSPredicatepredicateWithFormat:@"SELFMATCHES%@",strExpression];
- return[predicateevaluateWithObject:strDestination];
- }
- +(BOOL)isValidateEmail:(NSString*)email{
- NSString*strRegex=@"[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+.[A-Za-z]{1,5}";
- BOOLrt=[CommonToolsisValidateRegularExpression:emailbyExpression:strRegex];
- returnrt;
- }
- +(BOOL)isValidateTelNumber:(NSString*)number{
- NSString*strRegex=@"[0-9]{1,20}";
- BOOLrt=[CommonToolsisValidateRegularExpression:numberbyExpression:strRegex];
- returnrt;
- }
(7)NSDate进行筛选
- NSDate*endDate=[[NSDatedate]retain];
- NSTimeIntervaltimeInterval=[endDatetimeIntervalSinceReferenceDate];
- timeInterval-=3600*24*10;
- NSDate*beginDate=[[NSDatedateWithTimeIntervalSinceReferenceDate:timeInterval]retain];
- NSPredicate*predicate_date=
- [NSPredicatepredicateWithFormat:@"date>=%@ANDdate<=%@",beginDate,endDate];
- [fetchRequestsetPredicate:predicate_date];
- [endDaterelease];
- [beginDaterelease];
(编辑:李大同)
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