How to define the rules for type convert

[jzhw0130]

@martijnwalraven

Server define a type 'Date', the format is '2017-06-06' or 1496736244000, (string or int).
Generate the scheme.json by apollo-codegen download-schema, the type is 'Date', too

Generate the API.swift by apollo-codegen generate , the type convert to 'String' automatically. Then data decode will throw exception when server format is int(1496736244000). Because it can not convert 'Int' to 'String'..

Now I have to change the API.swift manually, from 'String' to 'Int'. But it is not good, I have to do it many times when scheme changes...

Could you tell me the best way to solve the problem?

Thanks a lot

Jing

[cerupcat]

Did you find a solution for this? I'm also looking how to automatically create Date types during apollo codegen.

[martijnwalraven]

@cerupcat @jzhw0130: You should be able to pass --passthrough-custom-scalars to apollo-codegen to avoid generating a typealias to String for custom scalars. You can then add your own alias and conversion code, see here for an example.

[cerupcat]

Awesome, thanks! Will take a look.

[jzhw0130]

@cerupcat I just modify the scheme.json manually to solve the problem

[cerupcat]

Thanks @jzhw0130. I don't think that would work for us since we share the schema file across platforms and it gets auto generated when we make changes. Will be giving the other solution a try when we get back to that part.

[shehang]

@jzhw0130 & @cerupcat Do you guys found a way to solve this?
I tried modifying the scheme.json file but it doesn't work.
Having trouble Decoding & Encoding DateTime type to Date in typealias.

Any help is appreciated.

[rickycpadilla]

I ran into a similar issue today and was able to find a solution.

Our schema had a custom scalar called Date. I wasn't able to make a type alias because Swift already obviously has type Date - plus, I wanted to convert the schema Date to Swift Date anyhow.

Here's what I did:

1. Add --passthroughCustomScalars to the build phase like below (see last line):

APOLLO_FRAMEWORK_PATH="$(eval find $FRAMEWORK_SEARCH_PATHS -name "Apollo.framework" -maxdepth 1)"

if [ -z "$APOLLO_FRAMEWORK_PATH" ]; then
echo "error: Couldn't find Apollo.framework in FRAMEWORK_SEARCH_PATHS; make sure to add the framework to your project."
exit 1
fi

cd "${SRCROOT}/${TARGET_NAME}"
$APOLLO_FRAMEWORK_PATH/check-and-run-apollo-cli.sh codegen:generate --queries="$(find . -name '*.graphql')" --passthroughCustomScalars --schema=schema.json API.swift

2. Add a Date extension like:

import Apollo

extension Date: JSONDecodable {
  public init(jsonValue value: JSONValue) throws {
    guard let isoString = value as? String else {
      throw JSONDecodingError.couldNotConvert(value: value, to: Date.self)
    }
    let formatter = ISO8601DateFormatter()
    formatter.formatOptions = [.withFractionalSeconds]
    guard let date = formatter.date(from: isoString) else {
      throw JSONDecodingError.couldNotConvert(value: value, to: Date.self)
    }
    self = date
  }
}

NOTE: Depending on the format of your ISO date string, you'll likely need to change formatter.formatOptions = [.withFractionalSeconds]. Our date strings have milliseconds, so I had to add these options for this to work.

[RolandasRazma]

Seeing people struggling with this, thought I will add my experience.
We have similar like @jzhw0130
Date format is '2017-06-06'
DateTime format is '2017-01-23T10:12:31Z' // ISO8601
Seconds format of 1496736244000 // Unix time stamp
and many other meaningless type like Markdown, VIDEO_ID etc that coming in string type

what we do is:

a) bash script to download and "transform" schema (with some comments):

# download new schema
apollo schema:download $SCHEMA_PATH --endpoint=$ENDPOINT_PATH

# strip down types we can't handle by representing them as strings 
# (they are represented as strings in JSON)
perl -i -0pe 's/("kind":\s*"SCALAR",\s*"name":\s*")(Date|Markdown|VIDEO_ID)(")/\1String\3/gms' $SCHEMA_PATH

# Unix timestamp (Seconds) is represented as "TimeInterval" in iOS 
# (in similar fashion you can "converting" your "Date" to "DateNoTime" if you want it to be typed in Swift)
perl -i -0pe 's/("kind":\s*"SCALAR",\s*"name":\s*")(Seconds)(")/\1TimeInterval\3/gms' $SCHEMA_PATH

b) Types.swift (in project)

public typealias DateTime = Date

extension DateTime: JSONDecodable, JSONEncodable {
    
    public init(jsonValue value: JSONValue) throws {
        guard let string = value as? String else {
            throw JSONDecodingError.couldNotConvert(value: value, to: String.self)
        }

        guard let date = ISO8601DateFormatter().date(from: string) else {
            throw JSONDecodingError.couldNotConvert(value: value, to: Date.self)
        }
        
        self = date
    }
    
    public var jsonValue: JSONValue {
        return ISO8601DateTimeFormatter.string(from: self)
    }
    
}

what this setup gives us is:
Date will be "String"
DateTime will be Swift "Date" (alias, decoded with our extension)
Seconds will be "TimeInterval" (decoded without any extension)

[designatednerd]

I've (finally) added some actual documentation and an example for this with #1474 - would appreciate any feedback.