NSPredicate
Cocoa提供了一个NSPredicate类,它用来指定过滤器的条件
原理类似于数据库查询
17.1 创建谓词
predicateWithFormat:
NSPredicate *predicate;
predicate = [NSPredicate predicateWithFormat:@"name == 'Herbie'"];
注意:如果谓词串中的文本块未被引用,则被看做是键路径,即需要用引号表明是字符串,单引号,双引号均可.键路径可以在后台包含许多强大的功能
计算谓词:
BOOL match = [predicate evaluateWithObject:car];
让谓词通过某个对象来计算自己的值,给出BOOL值
17.2 燃料过滤器
filteredArrayUsingPredicate:是NSArray数组的一种类别方法,循环过滤数组中的内容,将值为YES的对象累积到结果数组中返回
iphone编程应该密切注意谓词使用带来的性能问题
17.3 格式说明符
%d和%@等插入数值和字符串,%K表示key
还可以引入变量名,用$,类似环境变量,如:@"name == $NAME",再用predicateWithSubstitutionVariables调用来构造新的谓词(键/值字典),其中键是变量名,值是要插入的内容,注意这种情况下不能把变量当成键路径,只能用作值
17.4 运算符
17.4.1 比较和逻辑运算符
==等于
>:大于
>=和=>:大于或等于
<:小于
<=和=<:小于或等于
!=和<>:不等于
括号和逻辑运算AND、OR、NOT或者C样式的等效表达式&&、||、!
注意：不等号适用于数字和字符串
17.4.2 数组运算符
BETWEEN和IN后加某个数组，可以用{50,200}，也可以用%@格式说明符插入自己的对象，也可以用变量
17.5 SELF足够了
self就表示对象本身
17.6 字符串运算符
BEGINSWITH
ENDSWITH
CONTAINS
[c],[d],[cd],后缀表示不区分大小写，不区分发音符号，两这个都不区分
17.7 LIKE运算符
类似SQL的LIKES
LIKE，与通配符“*”表示任意多和“?”表示一个结合使用
LIKE也接受[cd]符号
MATCHES可以使用正则表达式
Car *makeCar (NSString *name, NSString *make, NSString *model, int modelYear, int numberOfDoors, float mileage, int horsepower) { Car *car = [[[Car alloc] init] autorelease]; car.name = name; car.make = make; car.model = model; car.modelYear = modelYear; car.numberOfDoors = numberOfDoors; car.mileage = mileage; Slant6 *engine = [[[Slant6 alloc] init] autorelease]; [engine setValue: [NSNumber numberWithInt: horsepower] forKey: @"horsepower"]; car.engine = engine; // Make some tires. // int i; for (int i = 0; i < 4; i++) { Tire * tire= [[[Tire alloc] init] autorelease]; [car setTire: tire atIndex: i]; } return (car); } // makeCar int main (int argc, const char * argv[]) { NSAutoreleasePool *pool; pool = [[NSAutoreleasePool alloc] init]; Garage *garage = [[Garage alloc] init]; garage.name = @"Joe's Garage"; Car *car; car = makeCar (@"Herbie", @"Honda", @"CRX", 1984, 2, 34000, 58); [garage addCar: car]; NSPredicate *predicate; predicate = [NSPredicate predicateWithFormat: @"name == 'Herbie'"]; BOOL match = [predicate evaluateWithObject: car]; NSLog (@"%s", (match) ? "YES" : "NO"); predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"]; match = [predicate evaluateWithObject: car]; NSLog (@"%s", (match) ? "YES" : "NO"); predicate = [NSPredicate predicateWithFormat: @"name == %@", @"Herbie"]; match = [predicate evaluateWithObject: car]; NSLog (@"%s", (match) ? "YES" : "NO"); predicate = [NSPredicate predicateWithFormat: @"%K == %@", @"name", @"Herbie"]; match = [predicate evaluateWithObject: car]; NSLog (@"%s", (match) ? "YES" : "NO"); 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"); car = makeCar (@"Badger", @"Acura", @"Integra", 1987, 5, 217036.7, 130); [garage addCar: car]; car = makeCar (@"Elvis", @"Acura", @"Legend", 1989, 4, 28123.4, 151); [garage addCar: car]; car = makeCar (@"Phoenix", @"Pontiac", @"Firebird", 1969, 2, 85128.3, 345); [garage addCar: car]; car = makeCar (@"Streaker", @"Pontiac", @"Silver Streak", 1950, 2, 39100.0, 36); [garage addCar: car]; car = makeCar (@"Judge", @"Pontiac", @"GTO", 1969, 2, 45132.2, 370); [garage addCar: car]; car = makeCar (@"Paper Car", @"Plymouth", @"Valiant", 1965, 2, 76800, 105); [garage addCar: car]; 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); NSArray *names; names = [results valueForKey:@"name"]; NSLog (@"%@", names); NSMutableArray *carsCopy = [cars mutableCopy]; [carsCopy filterUsingPredicate: predicate]; NSLog (@"%@", carsCopy); predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > %d", 50]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); predicateTemplate = [NSPredicate predicateWithFormat: @"engine.horsepower > $POWER"]; varDict = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt: 150], @"POWER", nil]; predicate = [predicateTemplate predicateWithSubstitutionVariables: varDict]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); 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); NSArray *names1 = [NSArray arrayWithObjects: @"Herbie", @"Badger", @"Judge", @"Elvis", nil]; NSArray *names2 = [NSArray arrayWithObjects: @"Judge", @"Paper Car", @"Badger", @"Phoenix", nil]; predicate = [NSPredicate predicateWithFormat: @"SELF IN %@", names1]; results = [names2 filteredArrayUsingPredicate: predicate]; NSLog (@"%@", predicate); NSLog (@"%@", results); return 0; predicate = [NSPredicate predicateWithFormat: @"modelYear > 1970"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); predicate = [NSPredicate predicateWithFormat: @"name contains[cd] 'er'"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); predicate = [NSPredicate predicateWithFormat: @"name beginswith 'B'"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); predicate = [NSPredicate predicateWithFormat: @"%K beginswith %@", @"name", @"B"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"with args : %@", results); predicateTemplate = [NSPredicate predicateWithFormat: @"name beginswith $NAME"]; NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys: @"Bad", @"NAME", nil]; predicate = [predicateTemplate predicateWithSubstitutionVariables:dict]; NSLog (@"SNORGLE: %@", predicate); predicate = [NSPredicate predicateWithFormat: @"name in { 'Badger', 'Judge', 'Elvis' }"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); predicateTemplate = [NSPredicate predicateWithFormat: @"name in $NAME_LIST"]; names = [NSArray arrayWithObjects:@"Badger", @"Judge", @"Elvis", nil]; dict = [NSDictionary dictionaryWithObjectsAndKeys: names, @"NAME_LIST", nil]; predicate = [predicateTemplate predicateWithSubstitutionVariables:dict]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); predicateTemplate = [NSPredicate predicateWithFormat: @"%K in $NAME_LIST", @"name"]; dict = [NSDictionary dictionaryWithObjectsAndKeys: names, @"NAME_LIST", nil]; predicate = [predicateTemplate predicateWithSubstitutionVariables:dict]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); NSLog (@"xSNORGLE: %@", predicate); // SELF is optional here. predicate = [NSPredicate predicateWithFormat:@"SELF.name in { 'Badger', 'Judge', 'Elvis' }"]; for (Car *car in cars) { if ([predicate evaluateWithObject: car]) { NSLog (@"SNORK : %@ matches", car.name); } } #if 0 predicate = [NSPredicate predicateWithFormat: @"ANY engine.horsepower > 200"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"SNORGLE: %@", predicate); #endif predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 200"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); predicate = [NSPredicate predicateWithFormat: @"[email protected] > 10"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); #if 0 predicate = [NSPredicate predicateWithFormat: @"ALL engine.horsepower > 30"]; results = [cars filteredArrayUsingPredicate: predicate]; NSLog (@"%@", results); #endif [garage release]; [pool release]; return (0); } // main判断字符串首字母是否为字母。
Objective-c代码
NSString *regex = @"[A-Za-z]+";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
if ([predicate evaluateWithObject:aString]) {
}