Fast, powerful, yet easy to use template engine for Go. Inspired by mako templates philosophy.
- Extremely fast. Templates are converted into Go code and then compiled.
- Almost all the bugs are caught during template compilation, so production suffers less from template-related bugs.
- Easy to use. See quickstart and examples for details.
- Powerful. Arbitrary Go code may be embedded into and mixed with templates. Be careful with this power - do not query db and/or external resources from templates unless you miss php way in Go :) This power is mostly for arbitrary data transformations.
- Easy to understand template inheritance powered by Go interfaces. See this example for details.
- Templates are compiled into a single binary, so there is no need in copying template files to the server.
- Templates cannot be updated on the fly on the server, since they are compiled into a single binary. Take a look at fasttemplate if you need fast template engine for simple dynamically updated templates.
Quicktemplate is more than 20x faster than html/template. The following simple template is used in the benchmark:
Benchmark results:
$ go test -bench=Template -benchmem ./tests
BenchmarkQuickTemplate1-4 10000000 158 ns/op 0 B/op 0 allocs/op
BenchmarkQuickTemplate10-4 2000000 604 ns/op 0 B/op 0 allocs/op
BenchmarkQuickTemplate100-4 300000 5498 ns/op 0 B/op 0 allocs/op
BenchmarkHTMLTemplate1-4 500000 2807 ns/op 752 B/op 23 allocs/op
BenchmarkHTMLTemplate10-4 100000 13527 ns/op 3521 B/op 117 allocs/op
BenchmarkHTMLTemplate100-4 10000 133503 ns/op 34499 B/op 1152 allocs/op
goTemplateBenchmark compares QuickTemplate with numerous go templating packages. QuickTemplate performs favorably.
By default all the template placeholders are html-escaped.
See examples.
Let's start with a minimal template example:
All the text outside function templates is treated as comments,
i.e. it is just ignored by quicktemplate compiler (qtc). It is for humans.
Hello is a simple template function.
{% func Hello(name string) %}
Hello, {%s name %}!
{% endfunc %}
Save this file into templates folder under the name hello.qtpl
and run qtc
inside this folder. qtc may be installed by issuing:
go get -u github.com/valyala/quicktemplate/qtc
If all went ok, hello.qtpl.go file must appear in the templates folder.
This file contains Go code for hello.qtpl. Let's use it!
Create a file main.go outside templates folder and put the following
code there:
package main
import (
"fmt"
"./templates"
)
func main() {
fmt.Printf("%s\n", templates.Hello("Foo"))
fmt.Printf("%s\n", templates.Hello("Bar"))
}Then run go run. If all went ok, you'll see something like this:
Hello, Foo!
Hello, Bar!
Let's create more complex template, which calls other template functions,
contains loops, conditions, breaks, continue and returns.
Put the following template into templates/greetings.qtpl:
Greetings greets up to 42 names.
It also greets John differently comparing to others.
{% func Greetings(names []string) %}
{% if len(names) == 0 %}
Nobody to greet :(
{% return %}
{% endif %}
{% for i, name := range names %}
{% if i == 42 %}
I'm tired to greet so many people...
{% break %}
{% elseif name == "John" %}
{%= sayHi("Mr. " + name) %}
{% continue %}
{% else%}
{%= Hello(name) %}
{% endif %}
{% endfor %}
{% endfunc %}
sayHi is unexported, since it starts with lowercase letter.
{% func sayHi(name string) %}
Hi, {%s name %}
{% endfunc %}
Note that every template file may contain arbitrary number
of template functions. For instance, this file contains Greetings and sayHi
functions.
Run qtc inside templates folder. Now the folder should contain
two files with Go code: hello.qtpl.go and greetings.qtpl.go. These files
form a single templates Go package. Template functions and other template
stuff is shared between template files located in the same folder.
So Hello template function may be used inside greetings.qtpl while
it is defined in hello.qtpl.
Moreover, the folder may contain ordinary Go files and its' contents may
be used inside templates.
Now put the following code into main.go:
package main
import (
"bytes"
"fmt"
"./templates"
)
func main() {
names := []string{"Kate", "Go", "John", "Brad"}
// qtc creates Write* function for each template function.
// Such functions accept io.Writer as first parameter:
var buf bytes.Buffer
templates.WriteGreetings(&buf, names)
fmt.Printf("buf=\n%s", buf.Bytes())
}Careful readers may notice different output tags were used in these
templates: {%s name %} and {%= Hello(name) %}. What's the difference?
The {%s x %} is used for printing html-safe strings, while {%= F() %}
is used for embedding template function calls. Quicktemplate supports also
other output tags:
{%d num %}for integers{%f float %}for float64{%z bytes %}for byte slices{%q str %}for json-compatible quoted strings.{%j str %}for embedding str into json string. Unlike{%q str %}it doesn't quote the string.{%u str %}for URL encoding the given str.{%v anything %}is equivalent to%vin printf-like functions.
All these output tags produce html-safe output, i.e. they escape < to <,
> to >, etc. If you don't want html-safe output, then just put = after
the tag. For example: {%s= "<h1>This h1 won't be escaped</h1>" %}.
As you may notice {%= F() %} and {%s= F() %} produce the same output for {% func F() %}.
But the first one is optimized for speed - it avoids memory allocations and copy.
So stick to it when embedding template function calls.
All the ouptut tags except of {%= F() %} may contain arbitrary valid
Go expression instead of just identifier. For example:
Import fmt for fmt.Sprintf()
{% import "fmt" %}
FmtFunc uses fmt.Sprintf() inside output tag
{% func FmtFunc(s string) %}
{%s fmt.Sprintf("FmtFunc accepted %q string", s) %}
{% endfunc %}
There are other useful tags supported by quicktemplate:
-
{% comment %}{% comment %} This is a comment. It won't trap into the output. It may contain {% arbitrary tags %}. They are just ignored. {% endcomment %} -
{% plain %}
{% plain %}
Tags will {% trap into %} the output {% unmodified %}.
Plain block may contain invalid and {% incomplete tags.
{% endplain %}
```
* `{% collapsespace %}`
```qtpl
{% collapsespace %}
<div>
<div>space between lines</div>
and {%s " tags" %}
<div>is collapsed into a single space
unless{% newline %}or{% space %}is used</div>
</div>
{% endcollapsespace %}
```
Is converted into
```
<div> <div>space between lines</div> and tags <div>is collapsed into a single space unless
or is used</div> </div>
```
* `{% stripspace %}`
```qtpl
{% stripspace %}
<div>
<div>space between lines</div>
and {%s " tags" %}
<div>is removed unless{% newline %}or{% space %}is used</div>
</div>
{% endstripspace %}
```
Is converted into
```
<div><div>space between lines</div>and tags<div>is removed unless
or is used</div></div>
```
* `{% switch %}`, `{% case %}` and `{% default %}`:
```qtpl
1 + 1 =
{% switch 1+1 %}
{% case 2 %}
2?
{% case 42 %}
42!
{% default %}
I don't know :(
{% endswitch %}
```
* `{% code %}`:
```qtpl
{% code
// arbitrary Go code may be embedded here!
type FooArg struct {
Name string
Age int
}
%}
```
* `{% import %}`:
```qtpl
Import external packages.
{% import "foo/bar" %}
{% import (
"foo"
bar "baz/baa"
) %}
```
* `{% interface %}`:
```qtpl
Interfaces allow powerful templates' inheritance
{%
interface Page {
Title()
Body(s string, n int)
Footer()
}
%}
PrintPage prints Page
{% func PrintPage(p Page) %}
<html>
<head><title>{%= p.Title() %}</title></head>
<body>
<div>{%= p.Body("foo", 42) %}</div>
<div>{%= p.Footer() %}</div>
</body>
</html>
{% endfunc %}
Base page implementation
{% code
type BasePage struct {
TitleStr string
FooterStr string
}
%}
{% func (bp *BasePage) Title() %}{%s bp.TitleStr %}{% endfunc %}
{% func (bp *BasePage) Body(s string, n int) %}
<b>s={%q s %}, n={%d n %}</b>
{% endfunc %}
{% func (bp *BasePage) Footer() %}{%s bp.FooterStr %}{% endfunc %}
Main page implementation
{% code
type MainPage struct {
// inherit from BasePage
BasePage
// real body for main page
BodyStr string
}
%}
Override only Body
Title and Footer are used from BasePage.
{% func (mp *MainPage) Body(s string, n int) %}
<div>
main body: {%s mp.BodyStr %}
</div>
<div>
base body: {%= mp.BasePage.Body(s, n) %}
</div>
{% endfunc %}
```
See [basicserver example](https://github.com/valyala/quicktemplate/tree/master/examples/basicserver)
for more details.
# Performance optimization tips
* Prefer calling `WriteFoo` instead of `Foo` when generating template output
for `{% func Foo() %}`. This avoids unnesessary memory allocation and a copy
for a `string` returned from `Foo()`.
* Prefer `{%= Foo() %}` instead of `{%s= Foo() %}` when embedding
a function template `{% func Foo() %}`. Though both approaches generate
identical output, the first approach is optimized for speed.
* Prefer using existing output tags instead of passing `fmt.Sprintf`
to `{%s %}`. For instance, use `{%d num %}` instead
of `{%s fmt.Sprintf("%d", num) %}`, because the first approach is optimized
for speed.
* Prefer using specific output tags instead of generic output tag
`{%v %}`. For instance, use `{%s str %}` instead of `{%v str %}`, since
specific output tags are optimized for speed.
* Prefer creating custom function templates instead of composing complex
strings by hands before passing them to `{%s %}`.
For instance, the first approach is slower than the second one:
```qtpl
{% func Foo(n int) %}
{% code
// construct complex string
complexStr := ""
for i := 0; i < n; i++ {
complexStr += fmt.Sprintf("num %d,", i)
}
%}
complex string = {%s= complexStr %}
{% endfunc %}
```
```qtpl
{% func Foo(n int) %}
complex string = {%= complexStr(n) %}
{% endfunc %}
// Wrap complexStr func into stripspace for stripping unnesessary space
// between tags and lines.
{% stripspace %}
{% func complexStr(n int) %}
{% for i := 0; i < n; i++ %}
num{% space %}{%d i %}{% newline %}
{% endfor %}
{% endfunc %}
{% endstripspace %}
```
* Make sure that the `io.Writer` passed to `Write*` functions
is [buffered](https://golang.org/pkg/bufio/#Writer).
This will minimize the number of `write`
[syscalls](https://en.wikipedia.org/wiki/System_call),
which may be quite expensive.
Note: There is no need in wrapping [fasthttp.RequestCtx](https://godoc.org/github.com/valyala/fasthttp#RequestCtx)
into [bufio.Writer](https://golang.org/pkg/bufio/#Writer), since it is already buffered.
* [Profile](https://blog.golang.org/profiling-go-programs) your programs
for memory allocations and fix top functions from
`go tool pprof --alloc_objects` output.
# FAQ
* *Why quicktemplate syntax is incompatible with [html/template](https://golang.org/pkg/html/template/)?*
Because `html/template` syntax isn't expressive enough for `quicktemplate`.
* *What's the difference between quicktemplate and [ego](https://github.com/benbjohnson/ego)?*
`Ego` is similar to `quicktemplate` in the sense it converts templates into Go code.
But it misses the following stuff, which makes `quicktemplate` so powerful
and easy to use:
* Defining multiple function templates in a single template file.
* Embedding function templates inside other function templates.
* Template interfaces, inheritance and overriding.
See [this example](https://github.com/valyala/quicktemplate/tree/master/examples/basicserver)
for details.
* Top-level comments outside function templates.
* Template packages.
* Combining arbitrary Go files with template files in template packages.
* Performance optimizations.
* *What's the difference between quicktemplate and [gorazor](https://github.com/sipin/gorazor)?*
`Gorazor` is similar to `quicktemplate` in the sense it converts templates into Go code.
But it misses the following useful features:
* Clear syntax insead of hard-to-understand magic stuff related
to template arguments, template inheritance and embedding function
templates into other templates.
* Performance optimizations.
* *I didn't find an answer for my question here*
Try exploring [these questions](https://github.com/valyala/quicktemplate/issues?q=label%3Aquestion).