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| author | Julien Tant | 2024-06-19 01:43:52 -0700 |
|---|---|---|
| committer | GitHub | 2024-06-19 10:43:52 +0200 |
| commit | dafb3daa12160c85639fedd3eacf5aaf51127c53 (patch) | |
| tree | 3070ec7a898edb927c77861f1747d1d06a7f9068 | |
| parent | a75b25333d94bef710bbc05a95baa2e77b61bca9 (diff) | |
| download | gomponents-dafb3daa12160c85639fedd3eacf5aaf51127c53.tar.lz gomponents-dafb3daa12160c85639fedd3eacf5aaf51127c53.tar.zst gomponents-dafb3daa12160c85639fedd3eacf5aaf51127c53.zip | |
Add an `Iff` helper (#172)
I ran into some situation where I want to conditionally render a node if
some variable is not nil and obviously I got a panic
```go
// package viewmodels
type SomePage struct {
s *string
}
// package views
func SomePage (vm viewmodels.SomePage) g,Node {
return Div(
If(vm.s == nil, Text("s is nil"),
If(vm.s !- nil, Text("s is " + vm.s), // this will panic when `s` is nil
)
}
```
In this situation, go will interpret the code of the second `if`
regardless of the condition because the code itself is not in a
condition.
This PR introduces a new `Iff` helper that accepts a callback. The
callback content is only interpreted when it's called, making the code
safe:
```go
// package viewmodels
type SomePage struct {
s *string
}
// package views
func SomePage (vm viewmodels.SomePage) g,Node {
return Div(
Iff(vm.s == nil, func () g.Node { return Text("s is nil") },
Iff(vm.s !- nil, func () g.Node { return Text("s is " + vm.s) },
)
}
```
I'm aware of the `Lazy` effort on the side, but I guess this is no a
breaking change and can still exist in addition to the `Lazy` effort.
Co-authored-by: Markus Wüstenberg <markus@maragu.dk>| -rw-r--r-- | gomponents.go | 11 | ||||
| -rw-r--r-- | gomponents_test.go | 29 |
2 files changed, 40 insertions, 0 deletions
diff --git a/gomponents.go b/gomponents.go index 7b73a3b..ae7cadc 100644 --- a/gomponents.go +++ b/gomponents.go @@ -254,9 +254,20 @@ func Group(children []Node) Node { // If condition is true, return the given Node. Otherwise, return nil. // This helper function is good for inlining elements conditionally. +// If your condition and node involve a nilable variable, use iff because +// go will evaluate the node regardless of the condition. func If(condition bool, n Node) Node { if condition { return n } return nil } + +// Iff execute the function f if condition is true, otherwise return nil. +// it is the preferred way to conditionally render a node if the node involves a nilable variable. +func Iff(condition bool, f func() Node) Node { + if condition { + return f() + } + return nil +} diff --git a/gomponents_test.go b/gomponents_test.go index 32304f3..df5da4f 100644 --- a/gomponents_test.go +++ b/gomponents_test.go @@ -284,3 +284,32 @@ func ExampleIf() { _ = e.Render(os.Stdout) // Output: <div><span>You lost your hat!</span></div> } + +func TestIff(t *testing.T) { + t.Run("returns node if condition is true", func(t *testing.T) { + n := g.El("div", g.Iff(true, func() g.Node { + return g.El("span") + })) + assert.Equal(t, "<div><span></span></div>", n) + }) + + t.Run("returns nil if condition is false", func(t *testing.T) { + n := g.El("div", g.Iff(false, func() g.Node { + return g.El("span") + })) + assert.Equal(t, "<div></div>", n) + }) +} + +func ExampleIff() { + var nillableVariable *struct { + str string + } + e := g.El("div", + g.Iff(nillableVariable != nil, func() g.Node { + return g.Text(nillableVariable.str) + }), + ) + _ = e.Render(os.Stdout) + // Output: <div></div> +} |