Objective-C NSPredicate

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);} // makeCarint 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 0predicate = [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: @"[e-mail] > 10"];    results = [cars filteredArrayUsingPredicate: predicate];    NSLog (@"%@", results);#if 0predicate = [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]) { 
}