NSPredicate使用

谓词(NSPredicate)

OC中的谓词操作是针对于数组类型的，他就好比数据库中的查询操作，数据源就是数组，这样的好处是我们不需要编写很多代码就可以去操作数组，同时也起到过滤的作用，我们可以编写简单的谓词语句，就可以从数组中过滤出我们想要的数据。非常方便。在Java中是没有这种技术的，但是有开源的框架已经实现了此功能。

下面看具体的例子。
Person.h

#import <Foundation/Foundation.h>

@interface Person : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) 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

下面看一下简单的用法

#import "ViewController.h"
#import "Person.h"

@interface ViewController ()

@property (nonatomic, strong) NSArray *persons;

@end

@implementation ViewController

- (NSArray *)persons
{
    if (_persons == nil) {
        self.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:@"我" andAge:80],
                        [Person personWithName:@"10" andAge:90],
                        [Person personWithName:@"1" andAge:20], nil];
    }
    return _persons;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age < %d", 30];
    // 查询name=1的并且age大于40
    predicate = [NSPredicate predicateWithFormat:@"name = '1' && age < %d", 40];
    
    // in 包含
    predicate = [NSPredicate predicateWithFormat:@"self.name IN {'1','2','4'} || self.age IN {30,40}"];
    
    // name 以m开头
    predicate = [NSPredicate predicateWithFormat:@"name BEGINSWITH 'm'"];
    
    // name 以c结尾
    predicate = [NSPredicate predicateWithFormat:@"name ENDSWITH 'a'"];
    
    // name 包含
    predicate = [NSPredicate predicateWithFormat:@"name CONTAINS '我'"];
    
    // like 匹配任意多个字符
    // name中只要有s字符就能满足条件
    predicate = [NSPredicate predicateWithFormat:@"name like '*我*'"];
    
    // ? 代表一个字符，*代表任意多个字符。下面的查询条件是：name中第二个字符是a,name有2个字符
    predicate = [NSPredicate predicateWithFormat:@"name like '?a'"];
    
    // name中第二个字符是a, name有任意多个字符
    predicate = [NSPredicate predicateWithFormat:@"name like '?a'"];
    
    
    NSArray *array = [self.persons filteredArrayUsingPredicate:predicate];
    
    
    NSLog(@"filterArray=%@", array);
    
}

@end

NSPredicate 中的运算符

从上面的例子中我们看到，创建谓词使用类方法predicateWithFormat: (NSString*) format，format 里的东西真的和SQL 的where 条件类似。另外，参数format 与NSLog 的格式化模版类似。另外谓词可以配合正则使用，功能强大。

1. 比较运算符 > 、< 、== 、 >= 、<= 、 !=

2. 逻辑运算符：AND、OR、NOT 这几个运算符计算并、或、非的结果。

3. 范围运算符：IN 、BETWEEN
   例：@"number BETWEEN {1,5}"
   @"address IN {'shanghai','nanjing'}"

4. 字符串本身:SELF
   例：@"SELF == 'APPLE'"

5. 字符串相关：BEGINSWITH、ENDSWITH、CONTAINS
   例： @"name CONTAINS[cd] 'ang'" //包含某个字符串
   @"name BEGINSWITH[c] 'sh'" //以某个字符串开头
   @"name ENDSWITH[d] 'ang'" //以某个字符串结束
   注:[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，也不区分发音符号。

6. 通配符：LIKE
   例：@"name LIKE[cd] 'er'" //代表通配符,Like也接受[cd].
   @"name LIKE[cd] '???er'"

7. 正则表达式：MATCHES
   例：NSString *regex = @"^A.+e$"; //以A开头，e结尾
   @"name MATCHES %@",regex

使用NSPredicate在两个数组之间进行差异筛选

NSArray* array = @[@"aa",@"bb"];
NSArray* array2 = @[@"aa",@"bb",@"cc",@"dd"];
NSPredicate* thePredicate = [NSPredicate predicateWithFormat:@"NOT(SELF in %@)",array];
NSArray* arr3 = [array2 filteredArrayUsingPredicate:thePredicate];
NSLog(@"%@",arr3);

// 输出结果
arr3={@"cc" ,@"dd"}

使用正则筛选一个数组

NSString *regex = @"^A.+e$";//以A 开头，以e 结尾的字符。
NSPredicate *pre= [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
if([pre evaluateWithObject: @"Apple"]){
    printf("YES\n");
}else{
    printf("NO\n");
}