在Swift中循环创建字典

Question

I have a variable set of objects that I need to place in a dictionary. I'm trying to add them to the dictionary in a for loop but from what I'm understanding dictionaries are immutable so they need to be declared immediately. How do I create a dictionary list of items that are not predetermined?

var newItems = [:]

for item in self.items{
  newItems["\(item.key)"]["name"] = "A new item" 
}

Answer 1

does not use the second value

var newItems : [String:String] = [:]

for i in 1..10{
  newItems[i.description] = "A new item" 
}

for more information https://www.weheartswift.com/dictionaries/

Answer 2

The problem with your original code is that dictionaries only have one key, so this construct newItems["\\(item.key)"]["name"] is syntactically incorrect. If you had a fixed number of properties you could use a struct and put that in a dictionary. As you posed the question, though, you need to create a dictionary where the stored elements themselves are dictionaries. So, although I didn't actually put this into Xcode, it's a template for what you need to do:

var newItems = [:[:]]()

for item in self.items {
    var itemDict = [:]()
    for prop in whereeveryourpropertiescomefrom {
        itemDict[prop] = valueforthisproperty
    }
    newItems["\(item.key)"] = itemDict        
}

Of course, if your properties were initially stored in a dictionary unique to this item (equivalent of the inner loop), just store it directly into newItems.

Then, you could reference things as

let value = newItems["\(item.key)"]?.["property key"]

Notice the dictionary retrieval returns an optional you have to deal with.

Answer 3

解决方案是初始化字典以创建另一个字典时

var newItems: [String:[String:AnyObject]]()