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):
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- NSPredicate *ca = [NSPredicate predicateWithFormat:(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*'" /
(6)邮箱验证、电话号码验证:
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- //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._%+-][email protected][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;
- }
(7)NSDate进行筛选
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- //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];