NSPredicate过滤器 用法
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- Cocoa用NSPredicate描述查询的方式,原理类似于在数据库中进行查询
- 计算谓词:
- //基本的查询
- NSPredicate *predicate;
- predicate = [NSPredicate predicateWithFormat: @"name == 'Herbie'"];
- BOOL match = [predicate evaluateWithObject: car];
- NSLog (@"%s", (match) ? "YES" : "NO");
- //在整个cars里面循环比较
- predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
- NSArray *cars = [garage cars];
- for (Car *car in [garage cars]) {
- if ([predicate evaluateWithObject: car]) {
- NSLog (@"%@", car.name);
- }
- }
- //输出完整的信息
- predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
- NSArray *results;
- results = [cars filteredArrayUsingPredicate: predicate];
- NSLog (@"%@", results);
- //含有变量的谓词
- 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作为路径名,因为它值代表值
- //谓词字符窜还支持c语言中一些常用的运算符
- 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"]);
- //强大的数组运算符
- 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运算符
- 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];//这里限制了SELF的范围
- NSLog (@"%@", results);
- //BEGINSWITH,ENDSWITH,CONTAINS
- //附加符号,[c],[d],[cd],c表示不区分大小写,d表示不区分发音字符,cd表示什么都不区分
- 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运算符(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);
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