File Validation

[xvendo]

I have created an filter on a FSCollection and used context based validation to achieve an error message based on a wrong file type. Is there an way to publish an error message from the onInvalid function, and would It be possible to add an example to the project README?

Files = new FS.Collection("files", { stores: [new FS.Store.GridFS("filesStore")] });

var myFilter = {
maxSize: 2000000, // in bytes
allow: {
contentTypes: ['image/*'], //allow only images in this FS.Collection
extensions: ['png']
},
onInvalid: function (message) {
SimpleSchema.messages({fileError: "File Error!"});
Context1.addInvalidKeys([{name: "fileId", type: "fileError"}]);
}
};

Files.filters(myFilter);