Golang unmarshal interface to struct. If you're allowed to change the data structure, .
Golang unmarshal interface to struct Unmarshal to decode that into a Message variable, the answer is {Cmd:create Data:map[conf:map[a:1] info:map[b:2]]}. The process of converting a map to a struct involves creating a new struct and I'd personally avoid this because I dislike so much obfuscation but if you really want a working xml. I am trying to create a generic method in Go that will fill a struct using data from a map[string]interface{}. Asking for help, clarification, or responding to other answers. This is my code: package main import ( "fmt" "encoding/json" ) type ServiceResult struct { Type string `json:"type"` Content interface{} `json:"content"` } type Person struct { Name string `json:"name"` } func main() { nikola := ServiceResult{} nikola. The Marshaling use to convert Go object into JSON and Unmarshal is JSON to Go Struct. (map[string]interface{}) Suppose we have a struct with interface field. type vehicle interface { vehicle() } type car struct { Type string Color string HP int Doors int } func (car) vehicle() { return } type plane struct { Type string Color string Engines int } func (plane) vehicle() { return } var _ vehicle = (*car)(nil) var _ vehicle = (*plane)(nil) of finding work-arounds (indeed I have several); this is a The problem here is that if you omit the type assertion here: new := v. Provide details and share your research! But avoid . . So we arrive at the top of the function, then we call Unmarshal() on f, and the json package checks if Foo has UnmarshalJSON() defined, and it does, so it calls it, and so on, to infinite recursion. interface to struct. To this end, I have another set of functions with a pre-defined signature that return the struct instances but since each function returns a different type of struct the function signature has interface{} as the return type. You can avoid the type assertion if instead of getting the Elem() you Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. When I send json. g: var msgMapTemplate interface{} err := json. Unmarshal will only set exported fields of the struct. The Different methods to convert map to struct in GO. Unmarshal([]byte(t. Unmarshal. golang json array unmarshal into type struct. Go: Unmarshalling JSON with multiple types. Unmarshal a concrete struct it . How to unmarshall Go struct field of type map[string]interface. Quick solution is unmarshal it to []map[string]interface{}, but then you need to convert it to struct manually. My problem is that the ‘properties’ → ‘help’ → ‘properties’ When working with interfaces in Go, it’s common to want to convert them to a concrete struct type. To unmarshal JSON into a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match. Now, let’s dive a bit type Outer struct { Inner Num int `json:"num"` } type Inner struct { Data string `json:"data"` } You lose some of the more granular capabilities you could have with a custom unmarshalling method, but when you're unmarshalling a struct with mostly primitive fields like strings, you really don't need to worry about that. 3. 1. Unmarshal of a struct with a field of type map[string]interface{} will fail with the error: golang unmarshal map[string]interface{} to a struct containing an array with meta. This doesn't seem to work with certain data types, like []byte. For example, in Java Json, we use the JsonTypeInfo annotation to specify the class type, refer to this. Second, we’ll unmarshal each element of the slice directly into our target array. This will allow the standard json package to do standard I am loading a json file (see specimen below) into a generic interface{} object and I want to convert it into a formal struct. If you have a JSON payload converted into map[string]interface{}, then the []byte field in the struct gets converted to a string. 0. Type = "Person" Use golang json unmarshal to parse JSON data with simple and complex structured data and unstructured data with examples In some cases, we do not know the structure of your JSON properties beforehand, so we This helped me as well. AssertEqual(err, nil) msgMap := msgMapTemplate. 4. Interface() The new is inferred to have a interface{} type. So Marshalling is the process of converting a Go data structure into a format that can be stored or transmitted, like JSON or XML. RawMessage, unmarshal the dynamic data conditionally in the switch and return the concrete structs that implement ReportContainer interface. How do I unmarshal it, knowing which implementation to use for interface field ? type Custom interface { Hash() string } type customImpl struct { hash string `json:"hash"` } func (c *customImpl) Hash string() { return c. To have Unmarshal() build a nested struct in Go, use a pointer to describe the child struct: var lists []List type List struct { With string Help []oList Element *List } I changed the example from the Unmarshal documentation to parse nested Animal data as a proof of concept: Keep the code you have now with json. For example, the method signature and usage might look like: func FillStruct(data map[string]interface{}, result interface{}) { } type MyStruct struct { Name string Age int64 } myData := make(map[string]interface{}) myData["Name"] = "Tony" myData["Age"] "Why would using just Foo cause recursion?" - @Chris The json package checks if a type has UnmarshalJSON() defined, and if so it calls that implementation. The problem is that xml. information between It is possible to do generic unmarshalling ala gson by decoding into an interface and then extracting a top level map from the result, e. I think this happens because, if you store a non-pointer object (like the DataWrapper{}) inside an interface, the "reflect" or type assertion can only get a duplicated object of the original non-pointer object, and thus couldn't assign values to your original one. ResponseBody), &msgMapTemplate) t. It seems mapstructure is not able to convert the string back into []byte, even though the struct clearly asks for []byte (you just get a nil for that field). Elem(). This is necessary when you need to access the underlying fields of the interface or In some marshal/unmarshal frameworks we need additional information to help the reflector. RawMessage type in our slice, rather than the empty interface. The first method is by using the type assertion operator “ (type)” to extract the underlying value from the interface and then manually mapping it to the fields The basic idea is that you unmarshal the source JSON directly into an interface, and then write custom code that performs type assertions on the unmarshalled interface in order to populate Unmarshal once to a interface{} and do all that annoying interface-casting to get the key that informs the type, then unmarshal again to the right type. Then when you take the address to unmarshal, the type of &new is *interface{} (pointer to interface{}) and unmarshal does not work as you expect. Unmarshalling is the reverse — taking data in 写代码时碰到这么一个需求，某个字段根据不同条件对应不同子结构体，通过interface返给前端，同时前端上传时也要通过这个字段将数据传给后端。 struct -> json这个比 First, we’ll use the json. Golang unable to map XML to Struct. So could I decode the JSON into a Message struct and change its Data's interface{} to type CreateMessage according to the Cmd? golang type conversion. When I use json. I want to write a function that receives several types of structs and unmarshals them from JSON. If you're allowed to change the data structure, golang type conversion. Alternatively, you could make a single You can use NewDecoder or Unmarshal functions of json package, and you can decode it to a struct or to a map[string]interface{} It depends on your preferences, but in this case, I prefer NewDecoder and struct combination. Unmarshal for your interfaces you could implement Unmarshaller. It would be pretty straight forward, figure out the type based on the XML elements, create a new instance of that type, unmarshal into that with the default unmarshaller, assign that to the interface field of your Stack Overflow for Teams Where developers & technologists share private knowledge with coworkers; Advertising & Talent Reach devs & technologists worldwide about your product, service or employer brand; OverflowAI GenAI features for Teams; OverflowAPI Train & fine-tune LLMs; Labs The future of collective knowledge sharing; About the company Visit the blog To unmarshal JSON into a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match. hash } type Order struct { A string `json:"a"` B int64 `json:"b"` A better approach will be to use struct for main schema and then use an slice of email struct for fetching the data for email entities get the values from the same according to requirements. We unmarshal the JSON back into a Person struct using json. For golang, you can implement the Unmarshaler interface for your own type yourself. Refer to How do I Unmarshal JSON? How can I unmarshal a JSON string into a struct, when the struct type is given in the JSON string. As a general solution — if, and only if, you can overcome this chicken-and-egg problem and make type parameters known at compile time, you can write a minimal generic Unmarshal once to a interface{} and do all that annoying interface-casting to get the key that informs the type, then unmarshal again to the right type. . 13. Alternatively, you could make a single struct that is a union of all the fields of all possible types. In Golang, a struct is a collection of fields, and a map is a collection of key-value pairs. Go’s nice type system handles matching the JSON properties back to the Person struct automatically. I want to improve the getCustomerFromDTO method in the code below, I need to create a struct from an interface {} and currently i need to marshall that interface to byte [] and Golang provides two main methods for converting an interface to a struct. This golang tutorial help to understand marshalling and un-marshalling of data using Golang. icohfnzpbzwvgxkzlmklvbppjwxfgfnaxbkgrcmsxxeomwpyjxonclmloidxkdtzghgnahonsqpaxvt