Nspredicate Query/Search

Description: The nspredicate in the cocoa Framework is used for querying, both in principle and in usage similar to where in SQL, which acts as a filter for the database.

The most commonly used function

+ (Nspredicate *) Predicatewithformat: (NSString *) Predicateformat, ...;

1. Compare operators >, <, = =, >=, <=,! =
Example: @ "number >= 99"

2. Scope operator: in, between
Example: @ "number between {1,5}"
@ "address in {' Shanghai ', ' Nanjing '}"

3. String itself: Self
Example: @ "self = = ' APPLE '"

4. String-Related: Beginswith, ENDSWITH, CONTAINS
Example: @ "name CONTAIN[CD] ' ang '"//contains a string
@ "name Beginswith[c] ' sh '"//start with a string
@ "name Endswith[d] ' ang '"//End with a string
Note: [C] is not case sensitive, [d] does not differentiate between pronounced symbols without accents, [CD] is neither case-sensitive, nor does it distinguish between pronounced symbols.

5. Wildcard characters: Like
Example: @ "name LIKE[CD] ' *er* '"//* represents a wildcard, like also accepts [CD].
@ "name LIKE[CD] '??? Er* ' "

6. Regular expression: MATCHES
Example: NSString *regex = @ "^a.+e$"; Start with a, E end
@ "Name MATCHES%@", regex

Practical application: Filter the Nsarray

Nsarray *array = [[Nsarray alloc]initwithobjects:@ "Beijing", @ "Shanghai", @ "Guangzou", @ "Wuhan", Nil];  NSString *string = @ "Ang";  Nspredicate *pred = [Nspredicate predicatewithformat:@ "Self CONTAINS%@", string];  NSLog (@ "%@", [array filteredarrayusingpredicate:pred]);  

Practical application: Determine if the first letter of the string is a letter

NSString *regex = @ "[a-za-z]+";  Nspredicate *predicate = [Nspredicate predicatewithformat:@ "Self MATCHES%@", regex];    if ([predicate evaluatewithobject:astring]) {  }  

Practical application: String substitution

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);  

Practical application: Intercepting strings

Assemble a string, you need to parse the URL inside  nsstring *[email protected] "<meta/><link/><title>1q84 book1</ Title>
Practical application: Judging mobile phone number, phone number function
Regular Judge mobile phone number address format-(BOOL) Ismobilenumber: (NSString *) mobilenum{/** * Mobile phone number * Move: 134[0-8],135,136,137,138,        139,150,151,157,158,159,182,187,188 * Unicom: 130,131,132,152,155,156,185,186 * Telecom: 133,1349,153,180,189 * *       NSString * MOBILE = @ "^1 (3[0-9]|5[0-35-9]|8[025-9]) \\d{8}$";         /** 10 * Mobile: China Mobile 11 * 134[0-8],135,136,137,138,139,150,151,157,158,159,182,187,188 */NSString * CM = @ "^1 (34[0-8]| (       3[5-9]|5[017-9]|8[278] \\d) \\d{7}$ "; /** 15 * Unicom: China Unicom * 130,131,132,152,155,156,185,186 * * N       sstring * CU = @ "^1 (3[0-2]|5[256]|8[56]) \\d{8}$"; /** 20 * China Telecom: Chinese Telecom * 133,1349,153,180,189 * * * NSString *       CT = @ "^1 ((33|53|8[09]) [0-9]|349) \\d{7}$";   /** 25 * Mainland China fixed and PHS 26 * Area code: 010,020,021,022,023,024,025,027,028,029 27      * Number: seven-bit or eight-bit * *//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; }}
Practical application: Mailbox verification, phone number verification
is a valid regular expression + (BOOL) isvalidateregularexpression: (NSString *) strdestination byexpression: (NSString *) strexpression {   Nspredicate *predicate = [nspredicatepredicatewithformat:@ "Self MATCHES%@", strexpression];     return [predicate evaluatewithobject:strdestination];} Verify 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;} Verify Phone + (BOOL) Isvalidatetelnumber: (NSString *) Number {   NSString *strregex = @ "[0-9]{1,20}";   BOOL RT = [Commontools isvalidateregularexpression:number Byexpression:strregex];   return RT;}
Practical application: NSDate to filter
Date within 10 days: nsdate *enddate = [[NSDate date] retain]; Nstimeinterval timeinterval= [endDate timeintervalsincereferencedate];timeinterval-=3600*24*10; NSDate *begindate = [[NSDate datewithtimeintervalsincereferencedate:timeinterval] retain];//filters the CoreData ( Suppose there are fetchrequest) nspredicate *predicate_date =[nspredicate predicatewithformat:@ "date >=%@ and date <=%@", Begindate,enddate];    [fetchrequest setpredicate:predicate_date];//Release retained Object [EndDate release]; [Begindate release];
Nspredicate Query/Search