首先舉一個例子：
匹配9-15個由字母/數字組成的字符串的正則表達式：
? ? NSString * regex = @"^[A-Za-z0-9]{9,15}$";
? ? NSPredicate *pred = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
? ? BOOL isMatch = [pred evaluateWithObject:txtfldPhoneNumber.text];
Cocoa用NSPredicate描述查詢的方式，原理類似于在數據庫中進行查詢
用BETWEEN，IN，BEGINWITH，ENDWITH，CONTAINS，LIKE這些謂詞來構造NSPredicate，必要的時候使用SELF直接對自己進行匹配
[cpp]?view plaincopy
?? NSPredicate?*predicate;?? predicate?=?[NSPredicate?predicateWithFormat:?@"name?==?'Herbie'"];?? ????BOOL?match?=?[predicate?evaluateWithObject:?car];?? ????NSLog?(@"%s",?(match)???"YES"?:?"NO");?? ?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"engine.horsepower?>?150"];?? ????NSArray?*cars?=?[garage?cars];?? ????for?(Car?*car?in?[garage?cars])?{?? ????????if?([predicate?evaluateWithObject:?car])?{?? ????????????NSLog?(@"%@",?car.name);?? ????????}?? ????}?? ?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"engine.horsepower?>?150"];?? ????NSArray?*results;?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ?? ????NSPredicate?*predicateTemplate?=?[NSPredicate?predicateWithFormat:@"name?==?$NAME"];?? ????NSDictionary?*varDict;?? ????varDict?=?[NSDictionary?dictionaryWithObjectsAndKeys:?? ???????????????@"Herbie",?@"NAME",?nil];?? ????predicate?=?[predicateTemplate?predicateWithSubstitutionVariables:?varDict];?? ????NSLog(@"SNORGLE:?%@",?predicate);?? ????match?=?[predicate?evaluateWithObject:?car];?? ??NSLog?(@"%s",?(match)???"YES"?:?"NO");?? ?? ?? ????? ????predicate?=?[NSPredicate?predicateWithFormat:?? ?????????????????@"(engine.horsepower?>?50)?AND?(engine.horsepower?<?200)"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"oop?%@",?results);?? ????? ????predicate?=?[NSPredicate?predicateWithFormat:?@"name?<?'Newton'"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?[results?valueForKey:?@"name"]);?? ?? ????predicate?=?[NSPredicate?predicateWithFormat:?? ?????????????????@"engine.horsepower?BETWEEN?{?50,?200?}"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ????? ????NSArray?*betweens?=?[NSArray?arrayWithObjects:?? ?????????????????????????[NSNumber?numberWithInt:?50],?[NSNumber?numberWithInt:?200],?nil];?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"engine.horsepower?BETWEEN?%@",?betweens];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ????predicateTemplate?=?[NSPredicate?predicateWithFormat:?@"engine.horsepower?BETWEEN?$POWERS"];?? ????varDict?=?[NSDictionary?dictionaryWithObjectsAndKeys:?betweens,?@"POWERS",?nil];?? ????predicate?=?[predicateTemplate?predicateWithSubstitutionVariables:?varDict];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"name?IN?{?'Herbie',?'Snugs',?'Badger',?'Flap'?}"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?[results?valueForKey:?@"name"]);?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"SELF.name?IN?{?'Herbie',?'Snugs',?'Badger',?'Flap'?}"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?[results?valueForKey:?@"name"]);?? ????? ????names?=?[cars?valueForKey:?@"name"];?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"SELF?IN?{?'Herbie',?'Snugs',?'Badger',?'Flap'?}"];?? ????results?=?[names?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ?? ?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"name?BEGINSWITH?'Bad'"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ????? ????predicate?=?[NSPredicate?predicateWithFormat:?@"name?BEGINSWITH?'HERB'"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ????? ????predicate?=?[NSPredicate?predicateWithFormat:?@"name?BEGINSWITH[cd]?'HERB'"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ?? ????predicate?=?[NSPredicate?predicateWithFormat:?@"name?LIKE[cd]?'*er*'"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results);?? ????? ????predicate?=?[NSPredicate?predicateWithFormat:?@"name?LIKE[cd]?'???er*'"];?? ????results?=?[cars?filteredArrayUsingPredicate:?predicate];?? ????NSLog?(@"%@",?results); ?
NSPredicate用于查詢和過濾
在SQL中作為查詢條件通常用WHERE，但在COREDATA中作為查詢條件就可以用到NSPredicate.
NSPredicate 不單可以和COREDATA中的FetchRequest 配合使用。也可以與NSArray配合使用。
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NSPredicate 中支持的關鍵詞和條件符：
1、>,<,>=,<=,= 比較運算符。
如：
???? NSPredicate * qcondition= [NSPredicate predicateWithFormat:@"salary >= 10000"];
2、字符串操作(包含)：BEGINSWITH、ENDSWITH、CONTAINS
如：
????????@"employee.name BEGINSWITH[cd] '李'" //姓李的員工
???? @"employee.name ENDSWITH[c] '夢'"?? //以夢結束的員工
???? @"employee.name CONTAINS[d] '宗'"?? //包含有"宗"字的員工
注:[c]不區分大小寫[d]不區分發音符號即沒有重音符號[cd]既不區分大小寫，也不區分發音符號。
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3、范圍：IN?? ，BWTEEN
如：
??? @"salary BWTEEN {5000,10000}"
??? @"em_dept IN '開發'"
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4、自身:SELF，這個只針對字符數組起作用。
如：
???? NSArray * test = =[NSArray arrayWithObjects: @"guangzhou", @"beijing", @"shanghai", nil];
???? @"SELF='beijing'"
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5、通配符：LIKE
???? LIKE 使用?表示一個字符，*表示多個字符，也可以與c、d 連用。
如：
???? @"car.name LIKE '?he?'" //四個字符中，中間為he
???? @"car.name LIKE '*jp'"?? //以jp結束
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6、正則表達式：MATCHES
如：
NSString *regex = @"^E.+e$";//以E 開頭，以e 結尾的字符。
NSPredicate *pre= [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
if([pre evaluateWithObject: @"Employee"]){
NSLog(@"matches YES");
}else{
NSLog(@"matches NO");
}
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7、邏輯運算符：AND、OR、NOT
如：
????? @"employee.name = 'john' AND employee.age = 28"
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8、占位符：
NSPredicate *preTemplate = [NSPredicate predicateWithFormat:@"name==$NAME"];
NSDictionary *dic=[NSDictionary dictionaryWithObjectsAndKeys:
@"Name1", @"NAME",nil];
NSPredicate *pre=[preTemplate predicateWithSubstitutionVariables: dic];
占位符就是字典對象里的key，因此你可以有多個占位符，只要key 不一樣就可以了。
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對數組過濾：
如：
?NSMutableArray?*carsCopy = [carsmutableCopy];
? ? [carsCopyfilterUsingPredicate: predicate];//filterUsingPredicate和NSMutableArray構成新數組。
? ??NSLog?(@"%@", carsCopy);
?? ?
? ? predicate = [NSPredicatepredicateWithFormat:@"engine.horsepower > %d",?50];
? ? results = [cars?filteredArrayUsingPredicate: predicate];
? ??NSLog?(@"%@", results);
總結
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