Cocoa用NSPredicate描述查詢的方式，原理類似于在數(shù)據(jù)庫中進行查詢
計算謂詞：
//基本的查詢
NSPredicate *predicate;
predicate = [NSPredicate predicateWithFormat: @"name == 'Herbie'"];
????BOOL match = [predicate evaluateWithObject: car];
????NSLog (@"%s", (match) ? "YES" : "NO");
//在整個cars里面循環(huán)比較
????predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
????NSArray *cars = [garage cars];
????for (Car *car in [garage cars]) {
????????if ([predicate evaluateWithObject: car]) {
????????????NSLog (@"%@", car.name);
????????}
????}
//輸出完整的信息
????predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
????NSArray *results;
????results = [cars filteredArrayUsingPredicate: predicate];
????NSLog (@"%@", results);
//含有變量的謂詞
????NSPredicate *predicateTemplate = [NSPredicate predicateWithFormat:@"name == $NAME"];
????NSDictionary *varDict;
????varDict = [NSDictionary dictionaryWithObjectsAndKeys:
???????????????@"Herbie", @"NAME", nil];
????predicate = [predicateTemplate predicateWithSubstitutionVariables: varDict];
????NSLog(@"SNORGLE: %@", predicate);
????match = [predicate evaluateWithObject: car];
??NSLog (@"%s", (match) ? "YES" : "NO");
//注意不能使用$VARIABLE作為路徑名，因為它值代表值
//謂詞字符竄還支持c語言中一些常用的運算符
???
????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"]);
//強大的數(shù)組運算符
????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);
//IN運算符
????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];//這里限制了SELF的范圍
????NSLog (@"%@", results);
//BEGINSWITH,ENDSWITH,CONTAINS
//附加符號，[c],[d],[cd],c表示不區(qū)分大小寫，d表示不區(qū)分發(fā)音字符，cd表示什么都不區(qū)分
????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);
//LIKE運算符（通配符）
????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);