NSDictionary按键排序为浮点数

Question

基本上我有一个带键和值的NSDictionary.

键都是数字,但目前它们是字符串.

我希望能够将它们作为数字进行比较,以便对它们进行排序.

例如:如果我有这样的词典:

{
  "100"  => (id)object,
  "20"   => (id)object,
  "10"   => (id)object,
  "1000" => (id)object,
}

我希望能够像这样对它进行排序:

{
  "10"   => (id)object,
  "20"   => (id)object,
  "100"  => (id)object,
  "1000" => (id)object,
}

有任何想法吗？

谢谢

汤姆

Answer 1

不确定你要做什么 - 词典本质上是未排序的,默认实现中没有稳定的键排序.如果要按排序键遍历值,可以执行以下操作:

NSInteger floatSort(id num1, id num2, void *context)
{
    float v1 = [num1 floatValue];
    float v2 = [num2 floatValue];
    if (v1 < v2)
        return NSOrderedAscending;
    else if (v1 > v2)
        return NSOrderedDescending;
    else
        return NSOrderedSame;
}

NSArray *allKeys = [aDictionary allKeys];
NSArray *sortedKeys = [allKeys sortedArrayUsingFunction:floatSort context:NULL];
for (id key in sortedKeys)
    id val = [aDictionary objectForKey:key];
    …

Answer 2

您无法对字典进行排序,但您可以将键作为数组获取,对其进行排序,然后按该顺序输出.sortedArrayUsingComparator将执行此操作,您可以将字符串与NSNumericSearch选项进行比较.

NSArray* keys = [myDict allKeys];
NSArray* sortedArray = [keys sortedArrayUsingComparator:^(id a, id b) { 
    return [a compare:b options:NSNumericSearch]; 
}]; 

for( NSString* aStr in sortedArray ) {
    NSLog( @"%@ has key %@", [myDict objectForKey:aStr], aStr );
}