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https://github.com/cardinalby/go-dto-merge
https://github.com/cardinalby/go-dto-merge
Last synced: about 5 hours ago
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- Host: GitHub
- URL: https://github.com/cardinalby/go-dto-merge
- Owner: cardinalby
- License: mit
- Created: 2024-02-06T10:18:26.000Z (9 months ago)
- Default Branch: master
- Last Pushed: 2024-02-17T17:26:50.000Z (9 months ago)
- Last Synced: 2024-02-17T18:32:10.150Z (9 months ago)
- Language: Go
- Size: 14.6 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
[](https://github.com/cardinalby/go-dto-merge/actions/workflows/test.yml)
[](https://github.com/cardinalby/go-dto-merge/actions/workflows/list.yml)
[](https://pkg.go.dev/github.com/cardinalby/go-dto-merge)
# dtomerge package
This package provides a way to deep merge two structs of the same type.
It's useful for merging **default** values with **user-provided** values (e.g. configs).
Values that are not present in the user-provided struct will be taken from the default struct.
**Only exported** fields are merged.
## Example
```
go get github.com/cardinalby/go-dto-merge
```
Example `Config` struct has a nested `UserConfig` struct.
```go
import "github.com/cardinalby/go-dto-merge"
type UserConfig struct {
Role string // for non-pointer fields zero value indicates it's not specified
Name string
}
type Config struct {
Verbose *bool // it is a pointer to distinguish between "not specified" and false
User UserConfig
}
```
Given defaults, we can merge them with user-provided values:
```go
// ptr is some helper function to create a pointer to a value
defaults := Config{ // it's called "src"
Verbose: ptr(true),
User: UserConfig{
Role: "admin",
Name: "John",
},
}
userProvided := Config{ // it's called "patch"
User: UserConfig{
Name: "Jane",
},
}
res, err := dtomerge.Merge(defaults, userProvided) // (src, patch)
// res == Config{
// Verbose: (*bool) true,
// User: UserConfig{
// Role: "admin",
// Name: "Jane",
// },
// }
```
## Pointers
Pointers can be used to distinguish between "not specified" and "explicit zero value" fields.
- If `patch` field contains a nil pointer, it will not override `defaults.Verbose`
- If `patch` field contains a pointer to zero value, it will override `src` field
only in case `src` pointer field is nil (value will be copied)
- If `patch` field contains a pointer tp **non**-zero value, it will override `src` field (value will be copied)
Use `dtomerge.OptDeRefPointers(false)` option to handle pointers as regular fields.
## Slices and maps
Setting additional option you can merge slices and maps as well.
```go
import (
"github.com/cardinalby/go-dto-merge"
"github.com/cardinalby/go-dto-merge/opt"
)
type Config struct {
Roles []string
Permissions map[string]bool
}
defaults := Config{
Roles: []string{"admin", "user"},
Permissions: map[string]bool{
"read": true,
"write": false,
},
}
userProvided := Config{
Roles: []string{"user", "guest"},
Permissions: map[string]bool{
"write": true,
},
}
res, err := dtomerge.Merge(defaults, userProvided,
// merge map keys
dtomerge.OptIterateMaps(true),
// merge slices as unique sets
dtomerge.OptMergeSlices(dtomerge.SlicesMergeStrategyUnique),
)
// res == Config{
// Roles: []string{"admin", "user", "guest"},
// Permissions: map[string]bool{
// "read": true,
// "write": true,
// },
// }
```
Possible `MergeSlices` strategies:
- `dtomerge.SlicesMergeStrategyUnique`: `[1, 2, 3] + [4, 2, 1] → [1, 2, 3, 4]`
- `dtomerge.SlicesMergeStrategyByIndex`: `[1, 2, 3] + [11, 12] → [11, 12, 3]`
- `dtomerge.SlicesMergeStrategyAtomic`: merge as a whole, default
## Other options
You can:
- specify a custom merge function for a specific type.
- specify a custom merge options for a specific type.
See [options godoc](https://pkg.go.dev/github.com/cardinalby/go-dto-merge#Options) for more details.