def initialize(bucket:,region:)
    @bucket = bucket
    client = Aws::S3::Client.new(region: region)
    @signer = Aws::S3::Presigner.new(client: client)
  end

  def sign(key,expires_in: 3600)
    @signer.presigned_url(:get_object,bucket: @bucket,key: key,expires_in: expires_in)
  end

NoMethodError - undefined method `credentials' for nil:NilClass:
  aws-sdk-core (2.1.15) lib/aws-sdk-core/signers/v4.rb:24:in `initialize'
  aws-sdk-core (2.1.15) lib/aws-sdk-core/s3/presigner.rb:88:in `block in sign_but_dont_send'

无用的错误消息表明您尚未配置AWS凭据.这些都需要生成签名.如果您使用客户端发送请求,您将收到一条更有用的错误消息,指出需要凭据.

def initialize(bucket:,region:)
  @bucket = bucket
  creds = Aws::Credentials.new('ACCESS_KEY','SECRET_ACCESS_KEY')
  client = Aws::S3::Client.new(region: region,credentials,creds)
  @signer = Aws::S3::Presigner.new(client: client)
end

def sign(key,expires_in: 3600)
  @signer.presigned_url(:get_object,expires_in: expires_in)
end

与您的问题无关,但您可以使用S3的资源接口来清理代码.

def initialize(bucket:,region:)
  @bucket = Aws::S3::Bucket.new(bucket,{
    region: region,credentials: Aws::Credentials.new('ACCESS_KEY','SECRET_ACCESS_KEY'),})
end

def sign(key,expires_in: 3600)
  @bucket.object(key).presigned_url(:get,expires_in: expires_in)
end

虽然我展示了如何在代码中配置凭据,但我强烈建议不要这样做.您应该在启动应用程序之前将凭据导出到ENV,或将它们放在共享凭证文件中.

$export AWS_ACCESS_KEY_ID=...
$export AWS_SECRET_ACCESS_KEY=...

或者将以下内容放在〜/ .aws / credentials中

[default]
aws_access_key_id=...
aws_secret_access_key=...

如果使用ENV或共享凭证文件,则不再需要在代码中配置它们.当SDK未提供给客户端构造函数时,SDK将尝试获取这些位置.