一般来说这种情况还是蛮多的，比如你从文件中读入了一个array1，然后想把程序中的一个array2中符合array1中内容的元素过滤出来。
正 常傻瓜一点就是两个for循环，一个一个进行比较，这样效率不高，而且代码也不好看。
其实一个循环或者无需循环就可以搞定了，那就需要用到NSPredicate这个类
1）例子一，循环过滤
我想过滤arrayContents的话只要循环 arrayFilter就好了
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#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSArray *arrayFilter = [NSArray arrayWithObjects:@"pict", @"blackrain", @"ip", nil];
NSArray *arrayContents = [NSArray arrayWithObjects:@"I am a picture.",
@"I am a guy", @"I am gagaga", @"ipad", @"iphone", nil];
int i = 0;
int count = (int)[arrayFilter count];
for(i = 0; i < count; i ++)
{
NSString *arrayItem = (NSString *)[arrayFilter objectAtIndex:i];
NSPredicate *filterPredicate = [NSPredicate predicateWithFormat:@"SELF CONTAINS %@", arrayItem];
NSLog(@"Filtered array with filter %@, %@", arrayItem, [arrayContents filteredArrayUsingPredicate:filterPredicate]);
}
}
return 0;
}
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输出结果是：
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| 2013-08-12 23:35:06.642 test[90135:303] Filtered array with filter pict, (
"I am a picture."
)
2013-08-12 23:35:06.644 test[90135:303] Filtered array with filter blackrain, (
)
2013-08-12 23:35:06.645 test[90135:303] Filtered array with filter ip, (
ipad,
iphone
)
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当然以上代码中arrayContent最好用mutable 的，这样就可以直接filter了，NSArray是不可修改的。
2）例子二，无需循环
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#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSArray *arrayFilter = [NSArray arrayWithObjects:@"abc1", @"abc3", nil];
NSArray *arrayContent = [NSArray arrayWithObjects:@"a1", @"abc1", @"abc4", @"abc2", nil];
NSPredicate *thePredicate = [NSPredicate predicateWithFormat:@"NOT (SELF in %@)", arrayFilter];
arrayContent = [arrayContent filteredArrayUsingPredicate:thePredicate];
NSLog(@"arrayContent = %@",arrayContent);
}
return 0;
}
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输出结果是：
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| 2013-08-12 23:34:36.653 test[90122:303] arrayContent = (
a1,
abc4,
abc2
)
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这样arrayContent过滤出来的就是不包含 arrayFilter中的所有item了。
3）生成文件路径下文件集合列表
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#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *defaultPath = [[NSBundle mainBundle] resourcePath];
NSError *error;
NSArray *directoryContents = [fileManager contentsOfDirectoryAtPath:defaultPath error:&error];
NSLog(@"directoryContents = %@",directoryContents);
}
return 0;
}
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输出结果是：
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| 2013-08-12 23:33:11.844 test[90093:303] directoryContents = (
test
)
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4）match的用法
- 简单比较
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#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *defaultPath = [[NSBundle mainBundle] resourcePath];
NSError *error;
NSArray *directoryContents = [fileManager contentsOfDirectoryAtPath:defaultPath error:&error];
NSLog(@"directoryContents = %@",directoryContents);
NSString *match = @"imagexyz-999.png";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF == %@", match];
NSArray *results = [directoryContents filteredArrayUsingPredicate:predicate];
NSLog(@"results = %@",results);
}
return 0;
}
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输出结果是：
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| 2013-08-12 23:41:50.130 test[90258:303] directoryContents = (
test
)
2013-08-12 23:41:50.132 test[90258:303] results = (
)
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- match里like的用法（类似Sql中的用法）
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#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *defaultPath = [[NSBundle mainBundle] resourcePath];
NSError *error;
NSArray *directoryContents = [fileManager contentsOfDirectoryAtPath:defaultPath error:&error];
NSLog(@"directoryContents = %@",directoryContents);
NSString *match = @"imagexyz*.png";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF like %@", match];
NSArray *results = [directoryContents filteredArrayUsingPredicate:predicate];
NSLog(@"results = %@",results);
}
return 0;
}
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输出结果是：
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| 2013-08-12 23:45:15.239 test[90312:303] directoryContents = (
test
)
2013-08-12 23:45:15.245 test[90312:303] results = (
)
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- 大小写比较
［c］表示忽略大小写，［d］表示忽略重音，可以在一起使用，如下：
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#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *defaultPath = [[NSBundle mainBundle] resourcePath];
NSError *error;
NSArray *directoryContents = [fileManager contentsOfDirectoryAtPath:defaultPath error:&error];
NSLog(@"directoryContents = %@",directoryContents);
NSString *match = @"imagexyz*.png";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF like [cd] %@", match];
NSArray *results = [directoryContents filteredArrayUsingPredicate:predicate];
NSLog(@"results = %@",results);
}
return 0;
}
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输出结果是：
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| 2013-08-12 23:46:29.758 test[90336:303] directoryContents = (
test
)
2013-08-12 23:46:29.764 test[90336:303] results = (
)
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4.使用正则
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#import <Foundation/Foundation.h>
int main(int argc, const char * argv[])
{
@autoreleasepool {
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *defaultPath = [[NSBundle mainBundle] resourcePath];
NSError *error;
NSArray *directoryContents = [fileManager contentsOfDirectoryAtPath:defaultPath error:&error];
NSLog(@"directoryContents = %@",directoryContents);
NSString *match = @"imagexyz-\\d{3}\\.png";
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF matches %@", match];
NSArray *results = [directoryContents filteredArrayUsingPredicate:predicate];
NSLog(@"results = %@",results);
}
return 0;
}
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输出结果是：
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| 2013-08-12 23:47:30.005 test[90358:303] directoryContents = (
test
)
2013-08-12 23:47:30.015 test[90358:303] results = (
)
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