[Swift4]Update templates for swift 4

[d-date]

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\.
• Filed the PR against the correct branch: 3.0.0 branch for changes related to OpenAPI spec 3.0. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming langauge.

Description of the PR

1. Updated Dependencies

Updated swift4 & 3 dependencies due to RxSwift 4.0.0 was released.

To build generated source code with ResponseAs=RxSwift in Swift 4, we need to build RxSwift 4.0.0 via Carthage / Cocoapods.

Also, Alamofire 4.5.1 is needed for Swift 4.

In this PR, I fixed minimum version for dependencies.

2. Update syntax for Swift 4

According SE-0110: Distinguish between single-tuple and multiple-argument function types
, we need to use tuple f(()) insted of f(),

so when function returns Observable<Void> type, we need to change onNext() to onNext(()).

3. Adoption for Codable

When using Codable, which is introduced on Swift4, with class inheritance, we must call try super.init(from: decoder) .

[wing328]

@d-date thanks for the PR.

cc @jgavris @ehyche @Edubits @jaz-ah

[d-date]

@wing328 @jgavris @ehyche @Edubits @jaz-ah
Added more improvement for swift syntax. please check it out.

[jgavris]

👍

[d-date]

@wing328 How about this PR?

[wing328]

@d-date let me review shortly and get back to you.

[ehyche]

I'll review tomorrow morning.

[wing328]

@d-date not related to this PR but the Petstore integration for Swift 4 client is already failing in the latest master. I wonder if you can take a look when you've time: #6944

(swift3 petstore integration tests passed without issue)

[d-date]

@wing328 I found that errors related to Codable, which is introduced on Swift4. The swift 4 pet store has little order sample models than generated ones. I’ll try to work on another issue, and fix on another PR, after merged this PR.

[wing328]

@d-date FYI. We've just merged #6672. Please pull the latest before trying to fix the Swift4 Petstore integration issue.

[d-date]

@wing328 finish fixing #6944

[d-date]

@wing328 cc @jgavris @ehyche @Edubits @jaz-ah
How about this PR?

[wing328]

@d-date when I ran ./run_xcodebuild.sh in samples/client/petstore/swift4/default/SwaggerClientTests, I got the following errors:

tended-module-overlay.yaml -Xcc -working-directory/tmp/swagger-codegen/samples/client/petstore/swift4/default/SwaggerClientTests/Pods
<unknown>:0: error: no such file or directory: '/tmp/swagger-codegen/samples/client/petstore/swift4/default/PetstoreClient/Classes/Swaggers/APIs/Fake_classname_tags123API.swift'
<unknown>:0: error: no such file or directory: '/tmp/swagger-codegen/samples/client/petstore/swift4/default/PetstoreClient/Classes/Swaggers/APIs/FakeclassnametagsAPI.swift'
Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc failed with exit code 1

** TEST BUILD FAILED **

(this error is different than the one I found in master)
Did you get similar errors when running the script locally?

(I don't think it's caused by this PR but would be nice if you can look into it)

[d-date]

@wing328 I found the reason why tests are failed. We cannot use object type in spec as Any in Swift4. The Codable is a kind of Protocol so that we can adopt for struct (f.e. String, Int) types, but Any is primitive, not struct.

As I read below, object is not written in type. How can I handle object in Swift4?
https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#data-types

I have alternative as below, but I don't know how to get whether dataType is object in mastache.

before:

open class func testInlineAdditionalPropertiesWithRequestBuilder(param: Any) -> RequestBuilder<Void> {
        let path = "/fake/inline-additionalProperties"
        let URLString = PetstoreClientAPI.basePath + path
        let parameters = JSONEncodingHelper.encodingParameters(forEncodableObject: param)
//Compile Error: cannot convert type
...
    }

After:

open class func testInlineAdditionalPropertiesWithRequestBuilder<T: Encodable>(param: T) -> RequestBuilder<Void> {
        let path = "/fake/inline-additionalProperties"
        let URLString = PetstoreClientAPI.basePath + path
        let parameters = JSONEncodingHelper.encodingParameters(forEncodableObject: param)
    }

[d-date]

already issued #6483

[wing328]

Please get some rest (I believe it's already late in Japan. 3am?) I'll take another look tomorrow

[wing328]

@jgavris @ehyche @Edubits @jaz-ah would you please take another look at this PR when you've time today?