OC中的謂詞操作是針對于數(shù)組類型的，他就好比數(shù)據(jù)庫中的查詢操作，數(shù)據(jù)源就是數(shù)組，這樣的好處是我們不需要編寫很多代碼就可以去操作數(shù)組，同時也起到過濾的作用，我們可以編寫簡單的謂詞語句，就可以從數(shù)組中過濾出我們想要的數(shù)據(jù)。非常方便。在Java中是沒有這種技術(shù)的，但是有開源的框架已經(jīng)實(shí)現(xiàn)了此功能。

下面來看一下具體的例子吧：
Person.h

  
#import <Foundation/Foundation.h>  
  
@interface Person : NSObject  
  
@property NSString *name;  
@property NSInteger age;  
  
+ (id)personWithName:(NSString *)name andAge:(NSInteger)age;  
  
@end  

Person.m

#import "Person.h"  
 
@implementation Person  
 
+ (id)personWithName:(NSString *)name andAge:(NSInteger)age{  
   Person *person = [[Person alloc] init];  
   person.name = name;  
   person.age = age;  
   return person;  
}  
 
- (NSString *)description{  
   NSString *s =[NSString stringWithFormat:@"name=%@,age=%ld",_name,_age];  
   return s;  
}  
 
@end  

我們在Person類中定義屬性，還有一個產(chǎn)生對象的類方法，同時重寫了description方法，用于打印結(jié)果

測試方法
main.m

#import <Foundation/Foundation.h>  
#import "Person.h"  

//謂詞，指定過濾器的條件，將符合條件的對象保留下來
//一般用謂詞過濾數(shù)組中指定的元素

int main(int argc, const charchar * argv[]) {  
    @autoreleasepool {  
         
        NSArray *persons = [NSArray arrayWithObjects:  
                            [Person personWithName:@"mac" andAge:20],  
                            [Person personWithName:@"1" andAge:30],  
                            [Person personWithName:@"2" andAge:40],  
                            [Person personWithName:@"3" andAge:50],  
                            [Person personWithName:@"4" andAge:60],  
                            [Person personWithName:@"5" andAge:70],  
                            [Person personWithName:@"6" andAge:20],  
                            [Person personWithName:@"7" andAge:40],  
                            [Person personWithName:@"8" andAge:60],  
                            [Person personWithName:@"9" andAge:40],  
                            [Person personWithName:@"0" andAge:80],  
                            [Person personWithName:@"10" andAge:90],  
                            [Person personWithName:@"1" andAge:20]];  
          
        //年齡小于30  
        //定義謂詞對象，謂詞對象中包含了過濾條件  
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age<%d",30];  
        //使用謂詞條件過濾數(shù)組中的元素，過濾之后返回查詢的結(jié)果  
        NSArray *array = [persons filteredArrayUsingPredicate:predicate];  
        NSLog(@"filterArray=%@",array);  
          
        //查詢name=1的并且age大于40  
        predicate = [NSPredicate predicateWithFormat:@"name='1' && age>40"];  
        array = [persons filteredArrayUsingPredicate:predicate];  
        NSLog(@"filterArray=%@",array);  
          
        //in(包含)  
        predicate = [NSPredicate predicateWithFormat:@"self.name IN {'1','2','4'} || self.age IN{30,40}"];  
          
        //name以a開頭的  
        predicate = [NSPredicate predicateWithFormat:@"name BEGINSWITH 'a'"];  
        //name以ba結(jié)尾的  
        predicate = [NSPredicate predicateWithFormat:@"name ENDSWITH 'ba'"];  
          
        //name中包含字符a的  
        predicate = [NSPredicate predicateWithFormat:@"name CONTAINS 'a'"];  
          
        //like 匹配任意多個字符  
        //name中只要有s字符就滿足條件  
        predicate = [NSPredicate predicateWithFormat:@"name like '*s*'"];  
        //?代表一個字符，下面的查詢條件是：name中第二個字符是s的  
        predicate = [NSPredicate predicateWithFormat:@"name like '?s'"];  
          
          
          
    }  
    return 0;  
}  
```
首先我們看到，我們初始化了一定大小的數(shù)組。
然后我們就可以使用NSPredicate類進(jìn)行過濾操作了

**1、查詢數(shù)組中年齡小于30的對象**
```
//年齡小于30  
//定義謂詞對象，謂詞對象中包含了過濾條件  
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age<%d",30];  
//使用謂詞條件過濾數(shù)組中的元素，過濾之后返回查詢的結(jié)果  
NSArray *array = [persons filteredArrayUsingPredicate:predicate];  
NSLog(@"filterArray=%@",array);  
```
首先創(chuàng)立一個過濾條件：

```

//定義謂詞對象，謂詞對象中包含了過濾條件  
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age<%d",30];  

這里面操作很簡單的：@"age<%d",這個age是Person的屬性名，%d相當(dāng)于占位符，然后后面用參數(shù)替換即可
然后進(jìn)行過濾操作，返回一個過濾之后的數(shù)組對象
``
//使用謂詞條件過濾數(shù)組中的元素，過濾之后返回查詢的結(jié)果  
NSArray *array = [persons filteredArrayUsingPredicate:predicate];  
```

**2、查詢name=1并且age大于40的集合**

```
//查詢name=1的并且age大于40  
predicate = [NSPredicate predicateWithFormat:@"name='1' && age>40"];  
array = [persons filteredArrayUsingPredicate:predicate];  
NSLog(@"filterArray=%@",array);  

當(dāng)然我們也可以使用&&進(jìn)行多條件過濾
```
**3、包含語句的使用**

```
//in(包含)  
predicate = [NSPredicate predicateWithFormat:@"self.name IN {'1','2','4'} || self.age IN{30,40}"];  
```
**4、指定字符開頭和指定字符結(jié)尾，是否包含指定字符**
```
//name以a開頭的  
predicate = [NSPredicate predicateWithFormat:@"name BEGINSWITH 'a'"];  
//name以ba結(jié)尾的  
predicate = [NSPredicate predicateWithFormat:@"name ENDSWITH 'ba'"];  
  
//name中包含字符a的  
predicate = [NSPredicate predicateWithFormat:@"name CONTAINS 'a'"];  
```
**5、like進(jìn)行匹配多個字符**
```
//like 匹配任意多個字符  
//name中只要有s字符就滿足條件  
predicate = [NSPredicate predicateWithFormat:@"name like '*s*'"];  
//?代表一個字符，下面的查詢條件是：name中第二個字符是s的  
predicate = [NSPredicate predicateWithFormat:@"name like '?s'"];  
```
**6NSCompoundPredicate進(jìn)行匹配多個條件**
```
 NSPredicate *preicate = [NSPredicate predicateWithFormat:@"name CONTAINS[c] %@", searchString];

//   NSLog(@"--->%@",[self.products filteredArrayUsingPredicate:preicate]);
    
    NSPredicate *preicate1 = [NSPredicate predicateWithFormat:@"age CONTAINS[c] %@", searchString];
//
//    NSLog(@"--->%@",[self.products filteredArrayUsingPredicate:preicate1]);
//    //多個條件
    NSPredicate *predicate = [NSCompoundPredicate orPredicateWithSubpredicates:@[preicate, preicate1]];
    NSLog(@"====--->%@",[persons filteredArrayUsingPredicate:predicate]);
```