NSPredicate谓词

NSPredicate可用于检索查询，是一个过滤容器，相当于数据库的where

基本用法

1.基本查询

注意：
如果谓词中的文本块没有被引用（单引号或双引号），则被当做是键路径，否则认为是字符串

//基本的查询NSPredicate *predicate;//方法一：predicate = [NSPredicate predicateWithFormat:@"name == 'Herbie'"];//方法二：predicate = [NSPredicate predicateWithFormat:@"name == %@", @"Herbie"];//方法三：%K表示keypredicate = [NSPredicate predicateWithFormat:@"%K == %@", @"name", @"Herbie"];BOOL match = [predicate evaluateWithObject:car];NSLog(@"%s", (match) ? "YES" : "NO");

//方法四：含有变量的谓词，注意不能使用$VARIABLE作为路径名，因为它值代表值，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NSPredicate *predicateTemplate = [NSPredicate predicateWithFormat:@"name == $NAME"];NSDictionary *varDict = [NSDictionary dictionaryWithObjectsAndKeys:@"Herbie", @"NAME", nil];predicate = [predicateTemplate predicateWithSubstitutionVariables:varDict];NSLog(@"predicate:==========%@", predicate);match = [predicate evaluateWithObject:self.car];NSLog (@"%s", (match) ? "YES" : "NO");

2.数组过滤匹配

集合(set)过滤：filteredSetUsingPredicate:

//输出完整的信息，在整个数组里寻找匹配的结果predicate = [NSPredicate predicateWithFormat:@"engine.horsepower > 150"];NSArray *results = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", results);

运算符

1.比较和逻辑运算符

符号 意义 == 等于 > 大于 >= (=>) 大于或等于 < 小于 <= (=<) 小于或等于 != (<>) 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

//输出完整的信息，在整个数组里寻找匹配的结果predicate = [NSPredicate predicateWithFormat:@"engine.horsepower > 150"];NSArray *results = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", results);//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 = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"C语言中一些常用的运算符~~~~~~~%@", results);//比较字符串的大小predicate = [NSPredicate predicateWithFormat:@"name < 'Newton'"];results = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", [results valueForKey: @"name"]);

2.数组运算符

BETWEEN和IN后加某个数组

//BETWEEN运算符//方法一：predicate = [NSPredicate predicateWithFormat:@"engine.horsepower BETWEEN {50, 200}"];results = [self.cars filteredArrayUsingPredicate: predicate];//获得result里对象的name的属性的集合NSArray *names = [results valueForKey:@"name"];NSLog (@"~~~~~~%@~~~~~~~~%@", results, names);//方法二：NSArray *betweens = [NSArray arrayWithObjects:[NSNumber numberWithInt: 50], [NSNumber numberWithInt: 200], nil];predicate = [NSPredicate predicateWithFormat:@"engine.horsepower BETWEEN %@", betweens];results = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", results);//方法三：predicateTemplate = [NSPredicate predicateWithFormat:@"engine.horsepower BETWEEN $POWERS"];varDict = [NSDictionary dictionaryWithObjectsAndKeys:betweens, @"POWERS", nil];predicate = [predicateTemplate predicateWithSubstitutionVariables:varDict];results = [self.cars filteredArrayUsingPredicate:predicate];NSLog (@"%@", results);//IN运算符//方法一：predicate = [NSPredicate predicateWithFormat:@"name IN {'Herbie', 'Snugs', 'Badger', 'Flap'}"];results = [self.cars filteredArrayUsingPredicate:predicate];NSLog (@"%@", [results valueForKey:@"name"]);//方法二：SELF表示自己predicate = [NSPredicate predicateWithFormat:@"SELF.name IN { 'Herbie', 'Snugs', 'Badger', 'Flap'}"];results = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", [results valueForKey: @"name"]);

3.字符串运算符

BEGINSWITH：以某个字符串开头

ENDSWITH：以某个字符串结束

CONTAINS：包含某个字符串

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 = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", results);predicate = [NSPredicate predicateWithFormat:@"name BEGINSWITH 'HERB'"];results = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", results);predicate = [NSPredicate predicateWithFormat:@"name BEGINSWITH[cd] 'HERB'"];results = [self.cars filteredArrayUsingPredicate: predicate];NSLog (@"%@", results);

4. LIKE和MATCHES运算符

LIKE：与通配符 “*” 和 “?”结合使用，也接受[cd]符号

“*”：表示任意多个字符匹配

“?”：表示一个字符匹配

MATCHES：可以使用正则表达式

self.car.name = @"hhher";//LIKE运算符（通配符）predicate = [NSPredicate predicateWithFormat:@"name LIKE[cd] '*er*'"];match = [predicate evaluateWithObject:self.car];NSLog (@"%s", (match) ? "YES" : "NO");predicate = [NSPredicate predicateWithFormat:@"name LIKE[cd] '???er*'"];match = [predicate evaluateWithObject:self.car];NSLog (@"%s", (match) ? "YES" : "NO");

5.合计操作

ANY，SOME：指定下列表达式中的任意元素。比如，ANY children.age < 18。

ALL：指定下列表达式中的所有元素。比如，ALL children.age < 18。

NONE：指定下列表达式中没有的元素。比如，NONE children.age < 18。它在逻辑上等于NOT (ANY …)。

IN：等于SQL的IN操作，左边的表达必须出现在右边指定的集合中。比如，name IN {‘Ben’, ‘Melissa’, ‘Nick’}。

复合谓词NSCompoundPredicate

创建复合谓词

[NSCompoundPredicate andPredicateWithSubpredicates:@[[NSPredicate predicateWithFormat:@"age > 25"], [NSPredicate predicateWithFormat:@"firstName = %@", @"Quentin"]]]; [NSPredicate predicateWithFormat:@"(age > 25) AND (firstName = %@)", @"Quentin"]; 

参考：

http://justsee.iteye.com/blog/1816971

http://nshipster.cn/nspredicate/