NSPredicate的用法
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 %@", between];
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);