ios - 如何使用ios， objective-c 获取与json中的对象具有相同引用号的所有值

Question

这是我在网络服务中的 json 响应的一部分。

- Books :[
 -{
     RfNo:"1",
     SegOrd:"1",
     LegNo:"1",
     Title:"wild elephants",
     Author:"Dr.Vijitha Perera",
     Country:"srilanka",
     Price:"$8.99"

  },
   -{
     RfNo:"1",
     SegOrd:"2",
     LegNo:"1",
     Title:"butterfly guide",
     Author:"Dr.Graham fox",
     Country:"united kingdom",
     Price:"$27.99"

  },
   -{
     RfNo:"1",
     SegOrd:"3",
     LegNo:"2",
     Title:"Beautiful birds",
     Author:"prof.saranath kotagama",
     Country:"India",
     Price:"$13.99"

  },
   -{
     RfNo:"1",
     SegOrd:"2",
     LegNo:"1",
     Title:"Nature life",
     Author:"prof.adam jules",
     Country:"USA",
     Price:"$22.99"

  },
   -{
     RfNo:"2",
     SegOrd:"1",
     LegNo:"1",
     Title:"Travel in japan",
     Author:"Mr.yon hoan",
     Country:"japan",
     Price:"$5.99"

  },
    -{
     RfNo:"2",
     SegOrd:"2",
     LegNo:"1",
     Title:"Journey To New York",
     Author:"Mr.Ben carlos",
     Country:"USA",
     Price:"$19.99"

  },
    -{
     RfNo:"2",
     SegOrd:"3",
     LegNo:"2",
     Title:"Life of Canada",
     Author:"Dr.aron parker",
     Country:"Canada",
     Price:"$11.99"

  },

我可以成功地将这些数据放入 NSMutableArray。但现在我想要的是将所有数据放入一个 arrya，它是 RfNo:"1"，无需others.that means I don't want RfNo:"2", all data with only RfNo:"1".我该怎么做。我把这个Books 从响应变成这样的 arrat。

NSDictionary *allResults = (NSDictionary *)resopnonse;//there isn't only the `Books` that is why I used Dictionary.

NSArray *books = [allResults objectForKey:@"Books"];
for(NSDictionary *all in books)
 {
   //so I want only the data which it's `RefNO:"1"`
 }

我该怎么做。希望得到你的帮助。

Answer 1

只需为此使用 NSPredicate。

NSArray *bookArray = allResults[@"Books"];

if (!bookArray) return;

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"RfNo == 1"];

NSArray *filteredArray = [bookArray filteredArrayUsingPredicate:predicate];

这将为您提供一系列 RfNo = 1 的书籍

第一个对象:filteredArray[0]

最后一个对象:[filteredArray lastObject]