I would like to check if a variable is a Char or Decimal. In Java, I would write the following. How would I do it in ESQL?
if (s instanceof String) {
// s is String
} else if (s instanceof Integer) {
// s is Integer value
}
As far as I know it is not possible in ESQL.
There is a FIELDTYPE function, but it does not give you the data type.
When programming in IIB you generally use the parsers to produce the message tree with fields in the correct data type, see for example XMLNSC data types when you work with XML messages. There was a similiar discussion here.
Related
As mentioned in Go specification:
"A type determines a set of values together with operations and methods specific to those values."
To introduce an operation or method to be applied on the values of a type,
Is that operation applied on values (taken from a set) supposed to give the result (or value) from the same set?
For example, in the below code, findName() is not supposed to be a method on type user. Instead findName() should be a helper function.
type user struct {
name string
email string
age int
}
func (u user) findElder(other user) user {
if u.age >= other.age {
return u
}
return other
}
func (u user) findName() string {
return u.name
}
"operations and methods specific to those values" does not mean that they are unique to those values, or that they result in those values.
According to Google, "specific" means "clearly defined or identified." In this quote from the Go spec, the word "specific" is used with regard to the fact that Go is strongly typed, meaning that operations and methods work on the types that they are defined or identified to work on.
For example, the == operator is specified to work on integer types, thus, the == operator is specific to values of int, int32, uint8, etc.
No, I don't think that the operation applied on values (taken from a set) are supposed to give the result (or value), only from the same set. They can be from a different set of values as well. It all depends on the use case, the design of the type and the operation.
So in your case, findName() can very well be a method even though it is returning something not in the set of input values.
I need to print all form requests to log, for later debugging. I need to have something like this, where formInput are different kind of structs. (All defined in my code.)
type SomeFormInput {
Name string
Age int
}
func handleForm(formInput interface{}) {
...
logger.Logf("%+v", formInput);
}
However, some of the forms contain "secret" data that needs to be sanitized before logging - specifically, passwords.
What is the best and easiest way to do this, without losing the generality of handleForm?
I still need it to accept interface{}.
I can use tags if needed.
type SomeFormInput struct {
Name string
Password string `hide:"true"` // something like this
}
There is no completely general solution to this. There are only specific solutions with different trade-offs.
Perhaps the most general solution would be to write a function that inspects each form type with reflection, and omits any sensitive fields in the output.
logger.Logf("%s", stripPassword(formInput));
This has the side effect of no longer using the %+v verb, which often won't matter, but if your type implements the fmt.Formatter interface, it will change behavior. But then again, your goal is to change behavior, so...
Which leads to a second option:
You could implement a custom Format() method on your type, to cause %+v (or %v or %s) to output whatever you desire (omitting private fields).
Along the same lines, but easier, if you're logging (or willing to log) JSON output, just impliment your own json.Marshaler for each type. Example:
func (i *SomeFormInput) MarshalJSON() ([]byte, error) {
intermediate := struct{
*SomeFormInput
Password struct{} `json:"-"` // Occlude Password field in the embedded struct
MarshalJSON struct{} `json:"-"` // Occlude MarshalJSON method on embedded struct, to avoid infinite loop
}{
SomeFormInput: i,
}
return json.Marshal(intermediate)
}
A similar option is to use the json:"-" tag for fields that should not be output. Example:
type SomeFormInput struct {
Name string
Password string `json:"-"`
}
And as a final option, you could filter the log output, prior to sending it to the logger. If you're using JSON, you could parse the data using the tokenizing json.Decoder, to omit only the keys you want. For arbitrary text, perhaps a regular expression could be used.
For most applications I work on, where I practically always use JSON logging, I would probably prefer option #4, followed by #5.
I am very new to Go and am trying to get my head around all the different types and how to use them. I have an interface with the following (which was originally in a json file):
[map[item:electricity transform:{fuelType}] map[transform:{fuelType} item:gas]]
and I have the following struct
type urlTransform struct {
item string
transform string
}
I have no idea how to get the interface data into the struct; I'm sure this is really stupid, but I have been trying all day. Any help would be greatly appreciated.
Decode the JSON directly to types you want instead of decoding to an interface{}.
Declare types that match the structure of your JSON data. Use structs for JSON objects and slices for JSON arrays:
type transform struct {
// not enough information in question to fill this in.
}
type urlTransform struct {
Item string
Transform transform
}
var transforms []urlTransform
The field names must be exported (start with uppercase letter).
Unmarshal the JSON to the declared value:
err := json.Unmarshal(data, &transforms)
or
err := json.NewDecoder(reader).Decode(&transforms)
From your response : [map[item:electricity transform:{fuelType}] map[transform:{fuelType} item:gas]].
As you can see here this is a an array that has map in it.
One way to get the value from this is :
values := yourResponse[0].(map[string]interface{}). // convert first index to map that has interface value.
transform := urlTransform{}
transform.Item = values["item"].(string) // convert the item value to string
transform.Transform = values["transform"].(string)
//and so on...
as you can see from the code above I'm getting the the value using map. And convert the value to the appropriate type in this case is string.
You can convert it to appropriate type like int or bool or other type. but this approach is painful as you need to get the value one bye one and assign it your your field struct.
I want to encode pointers differently than from values. Currently, if we have a struct:
type Order struct {
Item Tool
AssociatedItem *Tool
}
both get inlined into a Order document inside mongo when marshalling.
I need to be able to perform my own serialization in the case of a *Tool. For instance, I could in this case only store the Id for the Too instead of the whole content. Unfortunately the overriding mechanism in mgo is to define a SetBSON() GetBSON for the Tool but it doesn't differentiate between pointers and non pointers.
What would be the best way to handle this?
Use a different type for "pointers", for example:
type SelectiveTool Tool
func (st *SelectiveTool) SetBSON(raw bson.Raw) error {
return raw.Unmarshal(s)
}
type Order struct {
Item Tool
AssociatedItem *SelectiveTool
}
Whats the correct way in go to distinguish between when a value in a struct was never set, or is just empty, for example, given the following:
type Organisation struct {
Category string
Code string
Name string
}
I need to know (for example) if the category was never set, or was saved as blank by the user, should I be doing this:
type Organisation struct {
Category *string
Code *string
Name *string
}
I also need to ensure I correctly persist either null or an empty string to the database
I'm still learning GO so it is entirely possible my question needs more info.
The zero value for a string is an empty string, and you can't distinguish between the two.
If you are using the database/sql package, and need to distinguish between NULL and empty strings, consider using the sql.NullString type. It is a simple struct that keeps track of the NULL state:
type NullString struct {
String string
Valid bool // Valid is true if String is not NULL
}
You can scan into this type and use it as a query parameter, and the package will handle the NULL state for you.
Google's protocol buffers (https://code.google.com/p/goprotobuf/) use pointers to describe optional fields.
The generated objects provide GetFoo methods which take the pain away from testing for nil (a.GetFoo() returns an empty string if a.Foo is nil, otherwise it returns *a.Foo).
It introduces a nuisance when you want to write literal structs (in tests, for example), because &"something" is not valid syntax to generate a pointer to a string, so you need a helper function (see, for example, the source code of the protocol buffer library for proto.String).
// String is a helper routine that allocates a new string value
// to store v and returns a pointer to it.
func String(v string) *string {
return &v
}
Overall, using pointers to represent optional fields is not without drawbacks, but it's certainly a viable design choice.
The standard database/sql package provides a NullString struct (members are just String string and Valid bool). To take care of some of the repetitive work of persistence, you could look at an object-relational manager like gorp.
I looked into whether there was some way to distinguish two kinds of empty string just out of curiosity, and couldn't find one. With []bytes, []byte{} == []byte(nil) currently returns false, but I'm not sure if the spec guarantees that to always remain true. In any case, it seems like the most practical thing to do is to go with the flow and use NullString.