Object-C 学习笔记(三十二)--- 谓词:NSPredicate

最新推荐文章于 2020-05-24 01:09:39 发布

DRAGON-Yeah

最新推荐文章于 2020-05-24 01:09:39 发布

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文章标签：谓词 NSPredicate 匹配查询

本文链接：https://blog.youkuaiyun.com/dragonzard/article/details/17416811

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本文介绍了NSPredicate的基础概念及其在Objective-C中的应用实例。通过多个示例展示了如何利用NSPredicate进行数据过滤，包括基本条件筛选、格式占位符使用、运算符设定、关键字匹配及模糊查询等操作。

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谓词:NSPredicate:是一种过滤内容的匹配条件,与数据库下select语句操作相似.

举出一些常用的实例:

//
//  main.m
//  Predicate
//
//  Created by 5016 on 13-12-19.
//  Copyright (c) 2013年 dradon. All rights reserved.
//

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

//设置条件谓词
void conditionP(NSMutableArray *arr)
{
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age > 20"];
    
    for (Child *child in arr) {
        //表示指定的对象是否谓词条件
        if ([predicate evaluateWithObject:child]) {
            NSLog(@"%@",[child description]);
        }
    }
    NSLog(@"===================================================");
    NSArray *newArr = [arr filteredArrayUsingPredicate:predicate];
    for (Child *child in newArr) {
        NSLog(@"%@",[child description]);
    }
    
}

//设置格式占位符
void formatP(NSMutableArray *arr)
{
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@" age >= %d",20];
    for (Child *child in arr) {
        //表示指定的对象是否谓词条件
        if ([predicate evaluateWithObject:child]) {
            NSLog(@"%@",[child description]);
        }
    }
    NSLog(@"===================================================");
    NSArray *newArr = [arr filteredArrayUsingPredicate:predicate];
    for (Child *child in newArr) {
        NSLog(@"%@",[child description]);
    }
}

//设置运算符
void aluP(NSMutableArray *arr)
{
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age <= 22 && age >=20 "];
    
    NSLog(@"===================================================");
    NSArray *newArr = [arr filteredArrayUsingPredicate:predicate];
    for (Child *child in newArr) {
        NSLog(@"%@",[child description]);
    }
}

//设置关键字
void keyP(NSMutableArray *arr)
{
//    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name IN {'dragon-8','dragon-9'}"];
//    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name BEGINSWITH 'd'"];
//    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name endswith '2'"];
    
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name contains 'i'"];
    NSLog(@"===================================================");
    
    NSArray *newArr = [arr filteredArrayUsingPredicate:predicate];
    NSLog(@"newArr = %@ ",newArr);
}

//设置模糊查询
void likeP(NSMutableArray *arr)
{
    
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name like '*o*'"];
    NSLog(@"===================================================");
    
    NSArray *newArr = [arr filteredArrayUsingPredicate:predicate];
    NSLog(@"newArr = %@ ",newArr);
}


int main(int argc, const char * argv[])
{

    @autoreleasepool {
        
        //生成10个对象,装载到数组里
        NSMutableArray *arr = [NSMutableArray array];
        for (int i =0; i<10; i++) {
            Child *child = nil;
            if (i%2 == 0) {
                  child = [[Child alloc]initWithName:[NSString stringWithFormat:@"dragon-%d",i] andAge:16+i andSleep:90+i];
            }else{
                   child = [[Child alloc]initWithName:[NSString stringWithFormat:@"xoxixi-%d",i] andAge:10+i andSleep:70+i];
            }
            [arr addObject:child];
            [child release];
        }
        NSLog(@"arr = %@",arr);
        conditionP(arr);
        //formatP(arr);
        //aluP(arr);
        //keyP(arr);
        //keyP(arr);
        //likeP(arr);
    }
    return 0;
}