Cocoa过滤器NSPredicate的完全用法

最新推荐文章于 2025-08-08 15:26:30 发布

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最新推荐文章于 2025-08-08 15:26:30 发布

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分类专栏： iphone开发之数据部分文章标签： cocoa 正则表达式数据库 oop 优化语言

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本文深入探讨了Cocoa框架中的NSPredicate类，揭示了其在正则表达式和数据库查询中的强大应用。通过实例展示，如何利用NSPredicate简化字符串操作，提升代码效率。

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从下面的各个例子中，可以体会到NSPredicate的强大的能力，作为正则表达式的核心类，确实优化了很多的字符串及其正则相关的操作的流程。使代码简洁，而强大！

Cocoa用NSPredicate描述查询的方式，原理类似于在数据库中进行查询
计算谓词：
//基本的查询
NSPredicate *predicate;
predicate = [NSPredicate predicateWithFormat: @"name == 'Herbie'"];
    BOOL match = [predicate evaluateWithObject: car];
    NSLog (@"%s", (match) ? "YES" : "NO");

//在整个cars里面循环比较
    predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
    NSArray *cars = [garage cars];
    for (Car *car in [garage cars]) {
        if ([predicate evaluateWithObject: car]) {
            NSLog (@"%@", car.name);
        }
    }

//输出完整的信息
    predicate = [NSPredicate predicateWithFormat: @"engine.horsepower > 150"];
    NSArray *results;
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", results);

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

//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 = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"oop %@", results);
   
    predicate = [NSPredicate predicateWithFormat: @"name < 'Newton'"];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", [results valueForKey: @"name"]);

//强大的数组运算符
    predicate = [NSPredicate predicateWithFormat:
                 @"engine.horsepower BETWEEN { 50, 200 }"];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", results);
   
    NSArray *betweens = [NSArray arrayWithObjects:
                         [NSNumber numberWithInt: 50], [NSNumber numberWithInt: 200], nil];
    predicate = [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN %@", betweens];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", results);
    predicateTemplate = [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN $POWERS"];
    varDict = [NSDictionary dictionaryWithObjectsAndKeys: betweens, @"POWERS", nil];
    predicate = [predicateTemplate predicateWithSubstitutionVariables: varDict];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", results);

//IN运算符
    predicate = [NSPredicate predicateWithFormat: @"name IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", [results valueForKey: @"name"]);
    predicate = [NSPredicate predicateWithFormat: @"SELF.name IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", [results valueForKey: @"name"]);
   
    names = [cars valueForKey: @"name"];
    predicate = [NSPredicate predicateWithFormat: @"SELF IN { 'Herbie', 'Snugs', 'Badger', 'Flap' }"];
    results = [names filteredArrayUsingPredicate: predicate];//这里限制了SELF的范围
    NSLog (@"%@", results);
//BEGINSWITH,ENDSWITH,CONTAINS

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

//LIKE运算符（通配符）
    predicate = [NSPredicate predicateWithFormat: @"name LIKE[cd] '*er*'"];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", results);
   
    predicate = [NSPredicate predicateWithFormat: @"name LIKE[cd] '???er*'"];
    results = [cars filteredArrayUsingPredicate: predicate];
    NSLog (@"%@", results);

转自：有香烟没火柴的空间