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Swift如何优雅漂亮的打印字典、json

article 2024/9/20 12:30:56

Prettier debug output printing Swift Dictionary in Xcode

When I use print() on a dictionary in Swift, it comes out nice and pretty in the console, with a key and a value.

在Swift中，使用print()打印字典的时候，打印出来的样式如下

object = Optional({
customerId = 111;
transactionId = 333;
extraId = 444;
})

When I run po on that same dictionary, it spits out this nonsense dump which is incredibly hard to read.

当使用po 来打印同一个字典的时候，打印出来的另外一种更难阅读的样式如下：

▿ Optional<Any>
▿ some : 3 elements
▿ 0 : 2 elements
  ▿ .0 : transactionId
  - .1 : 333
▿ 1 : 2 elements
  ▿ .0 : customerId
  - .1 : 111
▿ 2 : 2 elements
  ▿ .0 : extraId
  - .1 : 444

Using just p is even worse

如果使用p来打印的话，看着更遭

(Any?) $R8 = some {
  payload_data_0 = 0x0000000170e679c0 {
  Swift._SwiftNativeNSDictionary = {}
  _heapBufferBridged_DoNotUse = 0x0000000170e679d0 {}
  nativeStorage = {
    buffer = 0x00000001703e4300 {
      Swift.ManagedBuffer = {}
    }
    initializedEntries = (values = 0x00000001703e4328, bitCount = 4)
    keys = 0x00000001703e4330
    values = 0x00000001703e4390
    }
  }
  payload_data_1 = 0x0000000000000000
  payload_data_2 = 0x0000000000000000
  instance_type = 0x0000000105ffc3f8
}

What can I do in the console to see my variables in a way that I can actually read them without having to sift through all this nonsense?

PS - In this case I am printing an Optional<Any> object that happens to be a dictionary, but it’s the same with a non-optional Dictionary.

解决方案如下：

第一种方案：

New answer (2021):

The fastest way to get readable output is to use:

po print(data)

Say, you have variable data like below:

let data: [String: Any] = ["value1": 64, "value2": true, "value3": "some"]

When you do po print(data), you will get following output:

(lldb) po print(data)
["value1": 64, "value2": true, "value3": "some"]
0 elements

If you’re not in a rush you can improve debug printing format following steps from answer in below.

OLD answer (2017):

expression debugPrint(object)
just put the line above in your debugger and hit enter. It will print out contents of our object in more human readable format.

also you can use another one command - po print(data), which is easier to remember.

第二种解决方案：

第一种方案只能给一个单行的打印出来

⚠️ The (previously) accepted answer only provided the dictionary as a non-formatted single line string like so:

Optional(["transactionId": 333, "customerId": 111, "extraId": 444])

➡️ As soon as you get more keys and embedded objects/dictionaries it becomes difficult to read.

PrettyPrint JSON solution

To get a nice json formatting (indentations, newlines, etc) you can define an alias (I named mine pjson) by running this command in your lldb terminal (source):

command regex pjson 's/(.+)/expr print(NSString(string: String(data: try! JSONSerialization.data(withJSONObject: %1, options: .prettyPrinted), encoding: .utf8)!))/'

You probably don’t want to re-define the alias everytime you open Xcode, so run the following command to append the alias definition to ~/.lldbinit:

echo "command regex pjson 's/(.+)/expr print(NSString(string: String(data: try! JSONSerialization.data(withJSONObject: %1, options: .prettyPrinted), encoding: .utf8)!))/'" >> ~/.lldbinit

This will create the pjson alias which you can use in your lldb terminal in Xcode:

pjson object

Comparing the outputs for the following Swift object:

let object: Any? = [
    "customerId": 111,
    "transactionId": 333,
    "extraId": 444,
    "embeddedDict": [
        "foo": true
    ]
]

❌ Output of po print(data)

Optional(["transactionId": 333, "embeddedDict": ["foo": true], "customerId": 111, "extraId": 444])

✅ Output of pjson

{
  "transactionId" : 333,
  "embeddedDict" : {
    "foo" : true
  },
  "customerId" : 111,
  "extraId" : 444
}

Improve this answer

edited Apr 22, 2021 at 0:10

pkamb

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answered Sep 15, 2020 at 21:28

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entering your permanent echo command in Terminal results in zsh: event not found: ))/and/or bash: !: event not found. Do you know the problem or how to fix?

– pkamb

Apr 22, 2021 at 16:40
2

@pkamb Looks like you’re running into this: serverfault.com/questions/208265/… Probably can be worked around by escaping some characters, but I’m not going to play that game. Instead, you can just copy the command (between the double quotes, or listed above), and add it to the ~/.lldbinit file.

– agirault

Apr 27, 2021 at 15:52
How can I get a value selected from the dictionary content?

– SimonKravis

Mar 28, 2022 at 1:04