生成此字符串的最佳方法是什么？ （...的NSMutableString）

Question

我有一个字典，其键是NSStrings，其对象是NSArray。这是一个例子：

key (NSString) : GroupA 
value (NSArray): John
                 Alex
                 Joe
                 Bob

有很多这样的条目，这只是一个例子。我需要做的是生成这样的字符串（例如：

(GroupA contains[cd] ('John' OR 'Alex' OR 'Joe' OR 'Bob')) AND (GroupB contains[cd] ('Starcraft' OR 'WOW' OR 'Warcraft' OR 'Diablo')) AND ..... 

我将把这个字符串提供给NSPredicate。生成此字符串的最佳方法是什么？我可以使用for循环，如果和所有这些，但是有更优雅的方式吗？ 感谢。

Answer 1

这不是一个有效的谓词格式字符串，所以即使你最终生成它，你也无法将其转换为NSPredicate

这就是你想要的：

NSDictionary *groupValuePairs = ....;

NSMutableArray *subpredicates = [NSMutableArray array];
for (NSString *group in groupValuePairs) {
  NSArray *values = [groupValuePairs objectForKey:group];
  NSPredicate *p = [NSPredicate predicateWithFormat:@"%K IN %@", group, values];
  [subpredicates addObject:p];
}

NSPredicate *final = [NSCompoundPredicate andPredicateWithSubpredicates:subpredicates];

这不具有你原来所暗示的案例和变音不敏感性。如果你确实需要，那么你需要更复杂一点：

NSDictionary *groupValuePairs = ....;

NSMutableArray *subpredicates = [NSMutableArray array];
for (NSString *group in groupValuePairs) {
  NSArray *values = [groupValuePairs objectForKey:group];
  NSMutableArray *groupSubpredicates = [NSMutableArray array];
  for (NSString *value in values) {
      NSPredicate *p = [NSPredicate predicateWithFormat:@"%K contains[cd] %@", group, value];
      [groupSubpredicates addObject:p];
  }
  NSPredicate *p = [NSCompoundPredicate orPredicateWithSubpredicates:groupSubpredicates];
  [subpredicates addObject:p];
}

NSPredicate *final = [NSCompoundPredicate andPredicateWithSubpredicates:subpredicates];

Answer 2

它应该是这样的

NSDictionary *myDict = [NSDictionary dictionaryWithObject:[NSArray arrayWithObjects:@"John",@"Alex",@"Joe",@"Bob",nil] forKey:@"GroupA"];
NSString *myString = @"(";

int j = 0;
for(NSString *key in [myDict allKeys]) {
    NSString *value = [myDict valueForKey:key];
    myString = [myString stringByAppendingFormat:@"%@ contains[cd] (", key];
    NSArray *myArray = (NSArray *)value;

    int idx = 0;
    for(NSString *name in myArray) {
        myString = [myString stringByAppendingFormat:@"'%@'",name];
        if(idx < [myArray count] - 1) {
            myString = [myString stringByAppendingFormat:@" OR "];
        } 
        idx++;
    }

    myString = [myString stringByAppendingString:@")"];

    if(j < [myDict count] -1) {
        myString = [myString stringByAppendingString:@" AND "];
    }

    j++;

};

myString = [myString stringByAppendingString:@")"];

NSLog(@"mystring %@",myString);