


Why Do I Get 'Type *T is Pointer to Type Parameter, Not Type Parameter' When Using Generics in Go?
Nov 05, 2024 pm 12:53 PMGo with Generics: Type *T is Pointer to Type Parameter, Not Type Parameter
Understanding Type Parameters and Constraints
When using generics in Go, it's crucial to distinguish between a type parameter and its constraint. A type parameter is denoted by a capital letter, such as T, while a constraint is an interface type that defines the behavior required by the type parameter. For instance:
<code class="go">type GS interface { Id() string SetId(string) }</code>
In this case, GS is the constraint, which specifies that a type implementing GS must have Id() and SetId() methods with specific signatures.
Type *T vs. Type Parameter
When using a type parameter like T in generics, it's essential to understand that *T is different from T. *T represents a pointer to the type parameter T.
Error Explanation
In your example, the error encountered is:
type *T is pointer to type parameter, not type parameter
This error occurs when trying to use a pointer method (SetId() in this case) on the type parameter (T). However, pointer methods are only available on the pointer to the type parameter (*T) and not on the type parameter本身.
Solving the Issue
To resolve this issue, you need to explicitly specify the constraint on the pointer to the type parameter. This can be done by adding an additional constraint:
<code class="go">type GS interface { Id() string SetId(string) } type PT interface { *GS }</code>
Now you can use PT as the constraint on MyStore:
<code class="go">type MyStore[T PT] struct { values map[string]T }</code>
Changing the occurrences of *T to T in the MyStore struct and method definition will also be necessary.
Implementation of the Constraint
The error message also indicates that the type A does not implement the GS interface because the SetId() method in A has a pointer receiver. To fix this, you need to ensure that the A type implements the GS interface correctly:
<code class="go">func (a *A) SetId(id string) { a.ID = id }</code>
With these modifications, the code should compile successfully.
The above is the detailed content of Why Do I Get 'Type *T is Pointer to Type Parameter, Not Type Parameter' When Using Generics in Go?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics











TointegrateGolangserviceswithexistingPythoninfrastructure,useRESTAPIsorgRPCforinter-servicecommunication,allowingGoandPythonappstointeractseamlesslythroughstandardizedprotocols.1.UseRESTAPIs(viaframeworkslikeGininGoandFlaskinPython)orgRPC(withProtoco

Golangofferssuperiorperformance,nativeconcurrencyviagoroutines,andefficientresourceusage,makingitidealforhigh-traffic,low-latencyAPIs;2.Python,whileslowerduetointerpretationandtheGIL,provideseasierdevelopment,arichecosystem,andisbettersuitedforI/O-bo

Golang is mainly used for back-end development, but it can also play an indirect role in the front-end field. Its design goals focus on high-performance, concurrent processing and system-level programming, and are suitable for building back-end applications such as API servers, microservices, distributed systems, database operations and CLI tools. Although Golang is not the mainstream language for web front-end, it can be compiled into JavaScript through GopherJS, run on WebAssembly through TinyGo, or generate HTML pages with a template engine to participate in front-end development. However, modern front-end development still needs to rely on JavaScript/TypeScript and its ecosystem. Therefore, Golang is more suitable for the technology stack selection with high-performance backend as the core.

TocompletelyuninstallGolang,firstdeterminehowitwasinstalled(packagemanager,binary,source,etc.),thenremoveGobinariesanddirectories,cleanupenvironmentvariables,anddeleterelatedtoolsandcaches.Beginbycheckinginstallationmethod:commonmethodsincludepackage

In Go language, channel is used for communication and synchronization between goroutines. Declare the use of make function, such as ch:=make(chanstring), send the ch

In Go, using select statements can effectively handle non-blocking channel operations and implement timeout mechanisms. Non-blocking reception or sending operations are realized through the default branch, such as 1. Non-blocking reception: if there is a value, it will be received and printed, otherwise the default branch will be executed immediately; 2. Non-blocking transmission: If there is no receiver in the channel, the sending will be skipped. In addition, timeout control can be implemented in conjunction with time.After, such as waiting for the result or returning after 2 seconds. You can also combine non-blocking and timeout behaviors, try to get the value immediately, and wait for a short time after failure, so as to improve the program's concurrent response capabilities.

When encountering a "cannotfindpackage" error, it is usually because Go cannot find the target package or dependency. The solution is as follows: 1. Check whether the import path is correct and ensure that it is consistent with the module path or directory structure; 2. Confirm that the go.mod file has been initialized and use gomodinit and gomodtidy to manage dependencies; 3. Run goget to download missing dependencies or clean the module cache; 4. Make sure to execute commands in the correct directory context, or specify the complete module relative path for construction.

In Go, if you want the structure field to use a custom field name when converting to JSON, you can implement it through the json tag of the structure field. 1. Use the json: "custom_name" tag to specify the key name of the field in JSON. For example, Namestringjson: "username"" will make the Name field output as "username"; 2. Add, omitempty can control that the output is omitted when the field is empty, such as Emailstringjson: "email,omitempty""
