Objective-C NSPredicate

原文

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

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

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

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

4 运算符

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

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

5 SELF足够了

self就表示对象本身

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

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

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: @"tires.@sum.pressure > 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]) {
}