[IOS开发]搜索用谓词NSPredicate

Cocoa提供了一个类NSPredicate类，该类主要用于指定过滤器的条件，该对象可以准确的描述所需条件，对每个对象通过谓词进行筛选，判断是否与条件相匹配。谓词表示计算真值或假值的函数。

NSPredicate *predicate;

predicate=[NSPredicatepredicateWithFormat:@"name=='Herbie'"];//用predicateWithFormat创建一个谓词，name作为键路径

BOOL match=[predicateevaluateWithObject:car];//car作为接收对象,evaluateWithObject返回一个bool值。

NSLog(@"%s",(match)?"YES":"NO");

predicate = [NSPredicatepredicateWithFormat:@"engine.horsepower
> 150"];

NSArray *cars = [garage cars];

for (Car *car in [garage cars])
{

if ([predicate evaluateWithObject:
car]) {

NSLog (@"%@",
car.name);

}

}
遍历cars判断是否是真，然后输出。

predicate = [NSPredicatepredicateWithFormat:@"engine.horsepower
> 150"];

NSArray *results;

results = [carsfilteredArrayUsingPredicate:
predicate];//它将循环过滤数组内容，根据谓词计算每个对象的值，并将值为YES的对象累计到将被返回的新数组中。

NSLog (@"%@", results);
filteredArrayUsingPredicate这个方法可以得到我们所需要的值。加上

NSArray *names;

names=[results valueForKey:@"name"];

NSLog (@"%@", names);
就和上面的值一样。

NSMutableArray *carsCopy = [carsmutableCopy];

[carsCopyfilterUsingPredicate:
predicate];//filterUsingPredicate和NSMutableArray构成新数组。

NSLog (@"%@", carsCopy);

predicate = [NSPredicatepredicateWithFormat:@"engine.horsepower
> %d", 50];

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

NSPredicate *predicateTemplate;

NSDictionary *varDict;

predicateTemplate = [NSPredicatepredicateWithFormat: @"engine.horsepower
> $POWER"];//创建一个键/值字典来存储，这里$符号用于变量

varDict = [NSDictionarydictionaryWithObjectsAndKeys:

[NSNumbernumberWithInt: 150],@"POWER", nil];//@后面参数名

predicate = [predicateTemplatepredicateWithSubstitutionVariables: varDict];

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

predicate = [NSPredicatepredicateWithFormat:

@"(engine.horsepower > 50) AND (engine.horsepower < 200)"];//可以运用运算符

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"oop %@", results);

predicate = [NSPredicatepredicateWithFormat:

@"engine.horsepower BETWEEN { 50, 200 }"];//这里可以运用between关键字。和上面效果一样

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

NSArray *betweens = [NSArray arrayWithObjects:

[NSNumbernumberWithInt: 50],
[NSNumbernumberWithInt: 200],nil];

predicate = [NSPredicatepredicateWithFormat: @"engine.horsepower
BETWEEN %@", betweens];

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

predicateTemplate = [NSPredicatepredicateWithFormat:@"engine.horsepower
BETWEEN $POWERS"];

varDict = [NSDictionarydictionaryWithObjectsAndKeys:
betweens, @"POWERS", nil];

predicate = [predicateTemplatepredicateWithSubstitutionVariables: varDict];//用变量

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

predicate = [NSPredicatepredicateWithFormat:@"name
< 'Newton'"];//不等号不仅可以用于数字，也可以用于字符串值。

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", [results valueForKey: @"name"]);

predicate = [NSPredicatepredicateWithFormat:@"name
IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];//包含在其中用IN

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", [results valueForKey: @"name"]);

predicate = [NSPredicatepredicateWithFormat:@"SELF.name
IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];//self关键字

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", [results valueForKey: @"name"]);

names = [cars valueForKey: @"name"];

predicate = [NSPredicatepredicateWithFormat:@"SELF
IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];//self关键字

results = [namesfilteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

predicate = [NSPredicatepredicateWithFormat:@"name
BEGINSWITH 'Bad'"];//字符串运算符BEGINSWITH,ENDSWITH,CONTAINS[c][d][cd]

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

BEGINSWITH：检查某个字符串是否以另一个字符串开头。

ENDSWITH：检查某个字符串是否以另一个字符串结尾。

CONTAINS：检查某个字符串是否以另一个字符串内部。

[c]不区分大小写[d]不区分发音符号即没有重音符号[cd]既不区分大小写，又不区分发音符号。

predicate = [NSPredicatepredicateWithFormat:@"name
LIKE[cd] '*er*'"];//*代表通配符Like还接受[cd].

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

predicate = [NSPredicatepredicateWithFormat:@"name
LIKE[cd] '???er*'"];//?只匹配一个字符并且还可以接受[cd].

results = [cars filteredArrayUsingPredicate: predicate];

NSLog (@"%@", results);

还可以使用MATCHES运算符。赋给该运算符一个正则表达式