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Possibility of private variables in substrate storage
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I want to store private variables in Substrate storage and I don't want to encode them. For example I have this structure and I want to store private variable in it.
pub struct TestStruct {
// Some public variables
// Could there be a private variable?
test_private: u64,
}
I understand that according to the idea in the blockchain, everything should be public, and that most likely the variable will need to be encrypted. I heard about the 'reveal pattern', does it help in this case?
I think you need to explain what is your usecase more precisely.
What does private variable means, who has access to it ?
As far as I know 'reveal pattern' is when you send the hash of what you will reveal, and then later you can reveal what was the original value, by checking the on-chain hash.
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I have this class here:
#Component
class UpdateRule(
private val rulesRepo: UpdateRuleRepo
) : UpdateRuleStoreGateway, UpdateRuleLoadGateway {
override fun store(rule: UpdatRule) {
//some code
}
override fun loadAll(): List<UpdateRule> {
//some code
}
Since I'm new to Spring and Kotlin, I'm not familiar with this syntax. What does the val inside the brackets mean (private val rulesRepo: UpdateRuleRepo) and what do the interfaces after the colon do (: UpdateRuleStoreGateway, UpdateRuleLoadGateway)? Is this Kotlin specific or Spring specific syntax and where can I read more about it?
This is Kotlin syntax, not Spring-specific.
What does the val inside the brackets mean (private val rulesRepo: UpdateRuleRepo)
The part between the parentheses () is the list of arguments for the primary constructor of the class. When a constructor argument is marked val or var, it also declares a property of the same name on the class.
In this case, it means rulesRepo is a constructor argument of the class UpdateRule, but also a property of that class. Since it's a val, it means the property is read-only (it only has a getter).
You can read more about this in the docs about constructors.
what do the interfaces after the colon do (: UpdateRuleStoreGateway, UpdateRuleLoadGateway)?
The types listed after the : in a class declaration are the parent classes (or interfaces) extended (or implemented) by that class. In this case it means UpdateRule implements both interfaces UpdateRuleStoreGateway and UpdateRuleLoadGateway.
This is described in the docs about implementing interfaces.
Val is var but final to put it simply. Final means it cannot be reassigned to another object/primitive data. But do keep it mind that it doesn't mean internal data is immutable. It's not like Python tuple! Individual element/member variables can be modified, but the whole thing cannot be reassigned(think of variable as a pointer, and it's referencing to the same object, although the internal details of the object may change over time)
Kotlin var is different from Java var by the way.
More on that here: https://www.baeldung.com/kotlin/java-kotlin-var-difference
I personally find kotlin var similar to TypeScript let.
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What is the difference between var and val in Kotlin?
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Closed 1 year ago.
I am learning Spring Boot with kotlin and I am so confused with the usage of var or val for entity property. In some tutorial they use val and the other use var. So I don't know which is the right one to declare property for entity. At least enlightenment me about this. Please & Thanks!!
val and var both are used to declare variables but the main difference between them could be defined as;
val: is used when you declare a variable with a value which you don't want to change or update, it is kind of a constant variable which can only be initialized once. And when you try to change its value, it will show an error like Val can not be reassigned. it is known as immutable variable in kotlin.
On the other hand,
var: is used when you intend to declare a general variable whose value could be changed or updated anywhere in the class. It could be initialized or reassigned multiple times and it is known as mutable variable in kotlin.
I hope this will help you. There is a good definition with example.
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I'm programming a piece of software that consumes APIs from different services and the methods would be the same but different execution. I wonder if the code can be organized in interfaces or I just keep working like this:
type endPoint struct{
serverName string
}
func (this *endPoint) getLastDateURL () string{
if this.Name ="A"{
return "api.someAWebsite.com/getLastDate"
}
if this.Name ="B"{
return "api.someBWebsite.com/getLastDate"
}
return ""
}
func (this *endPoint) processData () output{
if this.Name ="A"{
//process in some way
return
}
if this.Name ="B"{
//process in some different way
return
}
return
}
The interface alternative I'm thinking is about this:
struct endPoint interface{
getLastDateURL()
processData()
}
...
Do each method for each API provider
How would I use it then?
My end goal is to have maintainable and clean code. Honestly hate the fact that I'd have to write the same methods for each end point to implement the interface, but perhaps I do not have the Interface concept just so clear yet or there is little advantage in using interfaces in this case with again, the end goal of maintainable and clean code.
Thanks.
// "struct endPoint interface" is invalid, and signatures are missing their return types:
type endPoint interface{
getLastDateURL() string
processData() output
}
How would I use it then?
I can't give a complete solution since you haven't shown how you're using your current code, but in general you'd have:
Something that instantiates an implementation - whatever would be setting Name in the current implementation would instead create an instance of a concrete type implementing endPoint
Something that calls getLastDateURL and/or processData - instead of receiving an *endPoint struct, it would receive an endPoint interface value, and then wouldn't care what the underlying implementation is; it would just call the methods, pretty much just like it does today
My end goal is to have maintainable and clean code.
This is probably a good way to achieve that, but it depends on context not shown in the question.
Honestly hate the fact that I'd have to write the same methods for each end point to implement the interface
You're already writing an implementation for each end point, you're just writing them all in the same methods. The amount of code you have to write is almost identical, but the resulting code is cleaner & more organized - for example, each concrete implementation could be in its own file, rather than having to be all in the same methods. With many/complex providers, your current solution becomes increasingly difficult to navigate if you ever need to change it or add a provider.
Use the double dispatch pattern:
Define a typed func on endPoint for each class it supports.
Define an interface that has a func that accepts an endPoint object.
Have all classes that want to use endPoint implement that interface’s func and pass themselves to the typed endPoint method.
To invoke it, call the interface method passing endPoint.
IMHO you should do it.
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What's the meaning of interface{}?
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Closed 7 years ago.
Or what is the interface that all types implement?
I'm looking for something like the Object class in Java.
Is it possible for me to make my own kind of "Root" interface?
Any type that implements all the methods listed in the interface implements the interface.
The empty interface, interface{}, lists no methods. Therefore, all types implement it.
There is nothing "top level" about it however. Interfaces (although they can embed) do not have a hierarchical structure. The empty interface is simply a normal interface with no requirements.
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I am sure I am not the only one who's facing this problem but I am unable to find a solution till now. The problem is as below.
I have published a web service (on which I don't have any control and I cannot change it) from a legacy system and all the clients are using it. I receive requests from the web service and object which i get is a very complex one but for the sake of an example lets say I receive object A from the web service call which contains several other objects like Object B, Object C in it etc and in addition objects B & C also have some primitive data types as well as some other objects in them. My problem is that I want to validate the whole Object A (all the including objects and sub objects), which design pattern is recommended here? Secondly, the main point here is that I can get different types of Object A from the web service. What i really mean by different types of object A is that the Object A depends upon the client i.e. some clients will send Object A without filling the data in the containing Object B or even they can fill Object B partially and then send it in Object A. So I have to validate the Object A based on the client (as some clients will require containing Object B some will not, some will require few elements in Object B etc). So in other words I will have a place where I will also store the validation rules for each client which will tell me something like this that client ABC wants field abc in Object B to be of type string and the maximum length is 25 chars and it is mandatory to have data in that field.
Some validations which I would like to perform is
Checking fields of some object (say Object B) for data types, length of a particular field, is the field required for this client or is it optional etc etc...
Any concrete working example will be extremely useful.
The structure of the Object A for this particular example is as follows.
public class A
{
private B objectB;
private C objectC;
// and so on
}
public class B{
private E objectE;
private String name;
private int age;
// and so on
}
public class C
{
private F objectF;
private String address;
private String country;
}
public class E
{
// Members here
}
public class F
{
// Members here
}
P.S: I have given arbitrary names to the classes and the members just for the general understanding. O yes I forgot to mention that I am using java here but it doesn't really matter as the design principles or patterns can be applied to any language. Hoping to hear from you guys soon.. :)
Validation is a Cross Cutting Concern. There are several ways and several design patterns can be implemented.
In Asp.net it is being done via attributes, in Java Spring it is done via Annotations to keep the code clean, readable and maintainable.
You can find tons of different approaches, what you need to keep in mind is the approach of these frameworks follow. ie code maintenance, readability and clean code.
There is no silver bullet. You can even write validation in your code.
Each class should know how to validate itself. You can derive each class from an interface (say IValidatable) that has a .Validate() method. When you call .Validate() on object A, have it validate itself, and then call .Validate() on all children. Those children can validate themselves in a similar fashion.
I think this is a really simple version of the command pattern. Sort of.
You could also compose a Validator that you can attach to your class. The validator can know how to validate email addresses, regular addressess etc. This is a bit more extensible as you are basically creating a toolbox to attach to your class that only contains the tools it needs.