OC中的謂詞操作是針對于數組類型的，他就好比數據庫中的查詢操作，數據源就是數組，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，就可以從數組中過濾出我們想要的數據。非常方便。在Java中是沒有這種技術的，但是有開源的框架已經實現了此功能。

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下面來看一下具體的例子吧：

Person.h

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[objc]?view plaincopy

//??

//??Person.h??

//??46_NSPredicate??

//??

//??Created?by?jiangwei?on?14-10-18.??

//??Copyright?(c)?2014年?jiangwei.?All?rights?reserved.??

//??

??

#import?<Foundation/Foundation.h>??

??

@interface?Person?:?NSObject??

??

@property?NSString?*name;??

@property?NSInteger?age;??

??

+?(id)personWithName:(NSString?*)name?andAge:(NSInteger)age;??

??

@end??

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Person.m

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[objc]?view plaincopy

//??

//??Person.m??

//??46_NSPredicate??

//??

//??Created?by?jiangwei?on?14-10-18.??

//??Copyright?(c)?2014年?jiangwei.?All?rights?reserved.??

//??

??

#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，還有一個產生對象的類方法，同時重寫了description方法，用于打印結果

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測試方法

main.m

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[objc]?view plaincopy

//??

//??main.m??

//??46_NSPredicate??

//??

//??Created?by?jiangwei?on?14-10-18.??

//??Copyright?(c)?2014年?jiangwei.?All?rights?reserved.??

//??

??

#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組中的元素，過濾之后返回查詢的結果??

????????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組。

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然后我們就可以使用NSPredicate類進行過濾操作了

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1、查詢數組中年齡小于30的對象

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[objc]?view plaincopy

//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組中的元素，過濾之后返回查詢的結果??

NSArray?*array?=?[persons?filteredArrayUsingPredicate:predicate];??

NSLog(@"filterArray=%@",array);??

首先創立一個過濾條件：

?

?

[objc]?view plaincopy

//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相當于占位符，然后后面用參數替換即可

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然后進行過濾操作，返回一個過濾之后的數組對象

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[objc]?view plaincopy

//使用謂詞條件過濾數組中的元素，過濾之后返回查詢的結果??

NSArray?*array?=?[persons?filteredArrayUsingPredicate:predicate];??

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2、查詢name=1并且age大于40的集合

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[objc]?view plaincopy

//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);??

當然我們也可以使用&&進行多條件過濾

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3、包含語句的使用

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[objc]?view plaincopy

//in(包含)??

predicate?=?[NSPredicate?predicateWithFormat:@"self.name?IN?{'1','2','4'}?||?self.age?IN{30,40}"];??

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4、指定字符開頭和指定字符結尾，是否包含指定字符

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[objc]?view plaincopy

//name以a開頭的??

predicate?=?[NSPredicate?predicateWithFormat:@"name?BEGINSWITH?'a'"];??

//name以ba結尾的??

predicate?=?[NSPredicate?predicateWithFormat:@"name?ENDSWITH?'ba'"];??

??

//name中包含字符a的??

predicate?=?[NSPredicate?predicateWithFormat:@"name?CONTAINS?'a'"];??

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5、like進行匹配多個字符

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[objc]?view plaincopy

//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'"];??

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轉載于:https://www.cnblogs.com/shifu/p/4913339.html

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