発生したエラー

iphoneのシミュレータでデバックしようとすると下記のようなエラーが出る

エラー文①

Error output from Xcode build:
    objc[27479]: Class AMSupportURLConnectionDelegate is implemented in both ?? (0x1f5bfb8f0) and ?? (0x11acd02b8). One of the two will be used. Which
    one is undefined.
    objc[27479]: Class AMSupportURLSession is implemented in both ?? (0x1f5bfb940) and ?? (0x11acd0308). One of the two will be used. Which one is
    undefined.

エラー文②

Error output from CocoaPods:
    [!] Automatically assigning platform `iOS` with version `8.0` on target `Runner` because no platform was specified. Please specify a platform for
    this target in your Podfile.

解決策

Podfileが〜とエラー文が言っているので、Podfileを正しく動くものに入れ替える。
ios>podfile

# Uncomment this line to define a global platform for your project
# platform :ios, '9.0'

# CocoaPods analytics sends network stats synchronously affecting flutter build latency.
ENV['COCOAPODS_DISABLE_STATS'] = 'true'

project 'Runner', {
  'Debug' => :debug,
  'Profile' => :release,
  'Release' => :release,
}

def flutter_root
  generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'Generated.xcconfig'), __FILE__)
  unless File.exist?(generated_xcode_build_settings_path)
    raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure flutter pub get is executed first"
  end

  File.foreach(generated_xcode_build_settings_path) do |line|
    matches = line.match(/FLUTTER_ROOT\=(.*)/)
    return matches[1].strip if matches
  end
  raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Generated.xcconfig, then run flutter pub get"
end

require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)

flutter_ios_podfile_setup

target 'Runner' do
  use_frameworks!
  use_modular_headers!

  flutter_install_all_ios_pods File.dirname(File.realpath(__FILE__))
end

post_install do |installer|
  installer.pods_project.targets.each do |target|
    flutter_additional_ios_build_settings(target)
  end
end

参考になりそうなサイト

cacheを消して解決することもある