附加到[String:Any]字典结构中的数组 [英] Append to array in [String: Any] dictionary structure

问题描述

组装传递给 GRMustache.swift> a的数据有效载荷以渲染胡须模板，我处于一种需要的场景中将数据附加到先前在字典中定义的数组.

Assembling a data payload passed to GRMustache.swift for rendering mustache templates, I'm in a scenario where I need to append data to an array previously defined in the dictionary.

我的数据结构开始于:

var data: [String: Any] = [
    "key1": "example value 1",
    "key2": "example value 2",
    "items": [
        // I need to append here later
    ]
]

items键对是我以后需要在循环中附加的集合.

The items key pair is a collection I need to append later within a loop.

要添加到data["items"]数组中，我正在尝试类似的操作:

To add to the data["items"] array, I'm trying something like:

for index in 1...3 {
    let item: [String: Any] = [
        "key": "new value"
    ]

    data["items"].append(item)
}

此错误，因为类型Any?的值没有成员append，并且二进制运算符+=无法应用于类型Any?和[String : Any]的操作数.

This errors, as value of type Any? has no member append, and binary operator += cannot be applied to operands of type Any? and [String : Any].

这很有意义，因为我需要强制转换要附加的值；但是，我无法更改数组.

This makes sense, as I need to cast the value to append; however, I can't mutate the array.

投射到数组，是否强制向下转换会产生错误:

Casting to array, whether forcing downcast gives the error:

(data["items"] as! Array).append(item)

有吗?"不能转换为'Array< _>';您是要使用"as！"吗?强迫低垂?

'Any?' is not convertible to 'Array<_>'; did you mean to use 'as!' to force downcast?

不能在'Array< _>'类型的不可变值上使用变异成员

Cannot use mutating member on immutable value of type 'Array<_>'

似乎我的演员选错了；或者，也许我会以错误的方式来解决这个问题.

Seems like my cast is wrong; or, perhaps I'm going about this in the wrong way.

关于如何随着时间的推移逐步填充data["items"]的任何建议?

Any recommendation on how to fill data["items"] iteratively over time?

推荐答案

data[Items]的类型不是Array，实际上是Array<[String: Any]>.

The type of data[Items] isn't Array but actually Array<[String: Any]>.

您可以将其压缩为更少的步骤，但是我更喜欢多步操作的清晰性:

You could probably squeeze this into fewer steps, but I prefer the clarity of multiple steps:

var data: [String: Any] = [
    "key1": "example value 1",
    "key2": "example value 2",
    "items": []
]

for index in 1...3 {

    let item: [String: Any] = [
        "key": "new value"
    ]

    // get existing items, or create new array if doesn't exist
    var existingItems = data["items"] as? [[String: Any]] ?? [[String: Any]]()

    // append the item
    existingItems.append(item)

    // replace back into `data`
    data["items"] = existingItems
}

这篇关于附加到[String:Any]字典结构中的数组的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！