NSPRedicate valueForUndefinedKey

Question

我有一个ProductData的数组，如下所示，我想根据它们的category对它们进行过滤，并且我应用了以下Predicate，但它会返回错误。

pTempElements =[[NSMutableArray alloc] initWithArray: [self.pElements filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"category = %@", @"4"]]]; 

终止应用程序由于未捕获的异常“NSUnknownKeyException”， 原因：“[valueForUndefinedKey：]：此类 不是关键值编码兼容的关键类别”。

这里是pElements

po self.pElements 
<__NSArrayM 0x174241e30>(
<ProductData: 0x17427ce00>, 
<ProductData: 0x17427cd80>, 
<ProductData: 0x17427ce40>, 
<ProductData: 0x17427ce80>, 
) 

ProductData.m

#import "ProductData.h" 

@implementation ProductData 
@synthesize pId, pImage, pPrice, pName, pCategory 

-(id)initWithDictionary:(NSDictionary *)aDict{ 
    self = [self init]; 
    if (self){ 
     self.pId = [aDict objectForKey:@"id"]; 
     self.pPrice = [aDict objectForKey:@"price"]; 
     self.pImage = [aDict objectForKey:@"imagePath"]; 
     self.pCategory = [aDict objectForKey:@"category"]; 
     self.pName = [aDict objectForKey:@"name"]; 
    } 
    return self; 
} 

Answer 1

俯瞰你应该给由你打算阵列过滤的对象的属性名称。这里我猜这是pCategory。你应该重写你的代码如下

pTempElements =[[NSMutableArray alloc] initWithArray: [self.pElements filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"pCategory == %@", @"4"]]];