NSPredicate在CoreData中常用作查询使用，相当于sql语句中的where查询子句。
最常用的方法为：
NSPredicate *ca = [NSPredicate predicateWithFormat:(NSString *), ...];
比如我们要查询student表中name=“jjy”的信息，我们可以这样去用NSPredicate
NSEntityDescription * emEty = [NSEntityDescription entityForName:@"student" inManagedObjectContext:self.managedObjectContext];
NSFetchRequest *frq = [[NSFetchRequest alloc]init];
[frq setEntity:emEty];
NSPredicate * cdt = [NSPredicate predicateWithFormat:@"name= %@",@"jjy"];
[frq setPredicate:cdt];
NSArray *objs =[self.managedObjectContext executeFetchRequest:frq error:nil];
得到的就是名称为jjy的个人信息。
当然了这个还有其他用处，在网上看大针对其他用法的总结，在这借用过来，分享给大家：
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 = [[NSArray alloc]initWithObjects:@"beijing",@"shanghai",@"guangzou",@"wuhan", nil];
NSString *string = @"ang";
NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF CONTAINS %@",string];
NSLog(@"%@",[array filteredArrayUsingPredicate:pred]);
(2)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]) {
}
(3)字符串替换：
NSError* error = NULL;
NSRegularExpression* regex = [NSRegularExpression regularExpressionWithPattern:@"(encoding=\")[^\"]+(\")"
options:0
error:&error];
NSString* sample = @"<xml encoding=\"abc\"></xml><xml encoding=\"def\"></xml><xml encoding=\"ttt\"></xml>";
NSLog(@"Start:%@",sample);
NSString* result = [regex stringByReplacingMatchesInString:sample
options:0
range:NSMakeRange(0, sample.length)
withTemplate:@"$1utf-8$2"];
NSLog(@"Result:%@", result);
(4)截取字符串如下：
//组装一个字符串，需要把里面的网址解析出来
NSString *[email protected]"<meta/><link/><title>1Q84 BOOK1</title></head><body>";
//NSRegularExpression类里面调用表达的方法需要传递一个NSError的参数。下面定义一个
NSError *error;
//http+:[^\\s]* 这个表达式是检测一个网址的。(?<=title\>).*(?=</title)截取html文章中的<title></title>中内文字的正则表达式
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=title\\>).*(?=</title)" options:0 error:&error];
if (regex != nil) {
NSTextCheckingResult *firstMatch=[regex firstMatchInString:urlString options:0 range:NSMakeRange(0, [urlString length])];
if (firstMatch) {
NSRange resultRange = [firstMatch rangeAtIndex:0];
//从urlString当中截取数据
NSString *result=[urlString substringWithRange:resultRange];
//输出结果
NSLog(@"->%@<-",result);
}
}
(5)判断手机号码，电话号码函数
//组装一个字符串，需要把里面的网址解析出来
NSString *[email protected]"<meta/><link/><title>1Q84 BOOK1</title></head><body>";
//NSRegularExpression类里面调用表达的方法需要传递一个NSError的参数。下面定义一个
NSError *error;
//http+:[^\\s]* 这个表达式是检测一个网址的。(?<=title\>).*(?=</title)截取html文章中的<title></title>中内文字的正则表达式
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"(?<=title\\>).*(?=</title)" options:0 error:&error];
if (regex != nil) {
NSTextCheckingResult *firstMatch=[regex firstMatchInString:urlString options:0 range:NSMakeRange(0, [urlString length])];
if (firstMatch) {
NSRange resultRange = [firstMatch rangeAtIndex:0];
//从urlString当中截取数据
NSString *result=[urlString substringWithRange:resultRange];
//输出结果
NSLog(@"->%@<-",result);
}
}
(5)判断手机号码，电话号码函数
[cpp] view plaincopy
// 正则判断手机号码地址格式
- (BOOL)isMobileNumber:(NSString *)mobileNum
{
/**
* 手机号码
* 移动：134[0-8],135,136,137,138,139,150,151,157,158,159,182,187,188
* 联通：130,131,132,152,155,156,185,186
* 电信：133,1349,153,180,189
*/
NSString * MOBILE = @"^1(3[0-9]|5[0-35-9]|8[025-9])\\d{8}$";
/**
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;
}
}
(6)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._%+-][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
//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];
![详解STM32单片机的堆栈[图]](data:image/gif;base64,R0lGODlhAQABAIAAAP///wAAACwAAAAAAQABAAACAkQBADs=)