问题
### Error
```
NoMethodError - undefined method `size' for nil:NilClass
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:455:in `populate_mach_header'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:233:in `populate_fields'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:55:in `initialize_from_bin'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/macho_file.rb:33:in `new_from_bin'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:365:in `block in populate_machos'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:364:in `each'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:364:in `populate_machos'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:156:in `populate_fields'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho/fat_file.rb:95:in `initialize'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho.rb:31:in `new'
/Library/Ruby/Gems/2.6.0/gems/ruby-macho-1.4.0/lib/macho.rb:31:in `open'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/xcode/linkage_analyzer.rb:16:in `dynamic_binary?'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/sandbox/file_accessor.rb:171:in `block in vendored_dynamic_frameworks'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/sandbox/file_accessor.rb:170:in `select'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/sandbox/file_accessor.rb:170:in `vendored_dynamic_frameworks'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/sandbox/file_accessor.rb:179:in `vendored_static_frameworks'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/sandbox/file_accessor.rb:292:in `vendored_static_artifacts'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:82:in `each'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:82:in `flat_map'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:82:in `block (2 levels) in verify_no_static_framework_transitive_dependencies'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:74:in `each_key'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:74:in `block in verify_no_static_framework_transitive_dependencies'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:73:in `each'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:73:in `verify_no_static_framework_transitive_dependencies'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer/xcode/target_validator.rb:38:in `validate!'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer.rb:590:in `validate_targets'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/installer.rb:158:in `install!'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/command/install.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/claide-1.0.3/lib/claide/command.rb:334:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/lib/cocoapods/command.rb:52:in `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.9.1/bin/pod:55:in `
/usr/local/bin/pod:23:in `load'
/usr/local/bin/pod:23:in `
```
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[!] Oh no, an error occurred.
解决方案
flutter clean
rm -Rf ios/Pods
rm -Rf ios/.symlinks
rm -Rf ios/Flutter/Flutter.framework
rm -Rf ios/Flutter/Flutter.podspec
flutter build iOS