A fast, powerful, yet easy to use template engine for Go. Inspired by the Mako templates philosophy.
- Extremely fast. Templates are converted into Go code and then compiled.
- Quicktemplate syntax is very close to Go - there is no need to learn yet another template language before starting to use quicktemplate.
- Almost all 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 the database and/or external resources from templates unless you miss the PHP way in Go :) This power is mostly for arbitrary data transformations.
- Easy to use template inheritance powered by Go interfaces. See this example for details.
- Templates are compiled into a single binary, so there is no need to copy 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 a fast template engine for simple dynamically updated templates. There are ways to dynamically update the templates during development.
Quicktemplate is more than 20x faster than html/template. The following simple template is used in the benchmark:
Benchmark results:
$ go test -bench='Benchmark(Quick|HTML)Template' -benchmem github.com/valyala/quicktemplate/tests
BenchmarkQuickTemplate1-4 10000000 120 ns/op 0 B/op 0 allocs/op
BenchmarkQuickTemplate10-4 3000000 441 ns/op 0 B/op 0 allocs/op
BenchmarkQuickTemplate100-4 300000 3945 ns/op 0 B/op 0 allocs/op
BenchmarkHTMLTemplate1-4 500000 2501 ns/op 752 B/op 23 allocs/op
BenchmarkHTMLTemplate10-4 100000 12442 ns/op 3521 B/op 117 allocs/op
BenchmarkHTMLTemplate100-4 10000 123392 ns/op 34498 B/op 1152 allocs/op
goTemplateBenchmark compares QuickTemplate with numerous Go templating packages. QuickTemplate performs favorably.
- All template placeholders are HTML-escaped by default.
- Template placeholders for JSON strings prevent from
</script>-based XSS attacks:
{% func FailedXSS() %}
<script>
var s = {%q= "</script><script>alert('you pwned!')" %};
</script>
{% endfunc %}
See examples.
First of all, install the quicktemplate package
and quicktemplate compiler (qtc):
go get -u github.com/valyala/quicktemplate
go get -u github.com/valyala/quicktemplate/qtc
If you using go generate, you just need put following into your main.go
Important: please specify your own folder (-dir) to generate template file
//go:generate go get -u github.com/valyala/quicktemplate/qtc
//go:generate qtc -dir=app/views
Let's start with a minimal template example:
All 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 a templates folder under the name hello.qtpl
and run qtc inside this folder.
If everything went OK, hello.qtpl.go file should 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 issue go run. If everything went OK, you'll see something like this:
Hello, Foo!
Hello, Bar!
Let's create more a complex template which calls other template functions,
contains loops, conditions, breaks, continues 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 an 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, so its contents may
be used inside templates and vice versa.
The package name inside template files may be overriden
with {% package packageName %}.
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 int %}and{%dl int64 %}{%dul uint64 %}for integers.{%f float %}for float64. Floating point precision may be set via{%f.precision float %}. For example,{%f.2 1.2345 %}outputs1.23.{%z bytes %}for byte slices.{%q str %}and{%qz bytes %}for JSON-compatible quoted strings.{%j str %}and{%jz bytes %}for embedding str into a JSON string. Unlike{%q str %}, it doesn't quote the string.{%u str %}and{%uz bytes %}for URL encoding the given str.{%v anything %}is equivalent to%vin printf-like functions.
All the output tags except {%= F() %} 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 copies.
It is therefore recommended to stick to it when embedding template function calls.
Additionally, the following extensions are supported for {%= F() %}:
{%=h F() %}produces html-escaped output.{%=u F() %}produces URL-encoded output.{%=q F() %}produces quoted json string.{%=j F() %}produces json string without quotes.{%=uh F() %}produces html-safe URL-encoded output.{%=qh F() %}produces html-safe quoted json string.{%=jh F() %}produces html-safe json string without quotes.
All output tags except {%= F() %} family may contain arbitrary valid
Go expressions instead of just an 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 %}{% 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 %}{% 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> -
It is possible removing whitespace before and after the tag by adding
-after{%or prepending%}with-. For example:var sum int {%- for i := 1; i <= 3; i++ -%} sum += {%d i %} {%- endfor -%} return sumIs converted into:
var sum int sum += 1 sum += 2 sum += 3 return sum -
{% switch %},{% case %}and{% default %}:1 + 1 = {% switch 1+1 %} {% case 2 %} 2? {% case 42 %} 42! {% default %} I don't know :( {% endswitch %} -
{% code %}:{% code // arbitrary Go code may be embedded here! type FooArg struct { Name string Age int } %} -
{% package %}:Override default package name with the custom name {% package customPackageName %} -
{% import %}:Import external packages. {% import "foo/bar" %} {% import ( "foo" bar "baz/baa" ) %} -
{% cat "/path/to/file" %}:Cat emits the given file contents as a plaintext: {% func passwords() %} /etc/passwd contents: {% cat "/etc/passwd" %} {% endfunc %} -
{% interface %}: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 for more details.
-
Prefer calling
WriteFooinstead ofFoowhen generating template output for{% func Foo() %}. This avoids unnesessary memory allocation and a copy for astringreturned fromFoo(). -
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.Sprintfto{%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 example, 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:{% 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 %}{% 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.Writerpassed toWrite*functions is buffered. This will minimize the number ofwritesyscalls, which may be quite expensive.Note: There is no need to wrap fasthttp.RequestCtx into bufio.Writer, since it is already buffered.
-
Profile your programs for memory allocations and fix the most demanding functions based on the output of
go tool pprof --alloc_objects.
While the main quicktemplate purpose is generating HTML, it may be used for generating other data too. For example, JSON and XML marshalling may be easily implemented with quicktemplate:
{% code
type MarshalRow struct {
Msg string
N int
}
type MarshalData struct {
Foo int
Bar string
Rows []MarshalRow
}
%}
// JSON marshaling
{% stripspace %}
{% func (d *MarshalData) JSON() %}
{
"Foo": {%d d.Foo %},
"Bar": {%q= d.Bar %},
"Rows":[
{% for i, r := range d.Rows %}
{
"Msg": {%q= r.Msg %},
"N": {%d r.N %}
}
{% if i + 1 < len(d.Rows) %},{% endif %}
{% endfor %}
]
}
{% endfunc %}
{% endstripspace %}
// XML marshalling
{% stripspace %}
{% func (d *MarshalData) XML() %}
<MarshalData>
<Foo>{%d d.Foo %}</Foo>
<Bar>{%s d.Bar %}</Bar>
<Rows>
{% for _, r := range d.Rows %}
<Row>
<Msg>{%s r.Msg %}</Msg>
<N>{%d r.N %}</N>
</Row>
{% endfor %}
</Rows>
</MarshalData>
{% endfunc %}
{% endstripspace %}
Usually, marshalling built with quicktemplate works faster than the marshalling implemented via standard encoding/json and encoding/xml. See the corresponding benchmark results:
go test -bench=Marshal -benchmem github.com/valyala/quicktemplate/tests
BenchmarkMarshalJSONStd1-4 3000000 480 ns/op 8 B/op 1 allocs/op
BenchmarkMarshalJSONStd10-4 1000000 1842 ns/op 8 B/op 1 allocs/op
BenchmarkMarshalJSONStd100-4 100000 15820 ns/op 8 B/op 1 allocs/op
BenchmarkMarshalJSONStd1000-4 10000 159327 ns/op 59 B/op 1 allocs/op
BenchmarkMarshalJSONQuickTemplate1-4 10000000 162 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalJSONQuickTemplate10-4 2000000 748 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalJSONQuickTemplate100-4 200000 6572 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalJSONQuickTemplate1000-4 20000 66784 ns/op 29 B/op 0 allocs/op
BenchmarkMarshalXMLStd1-4 1000000 1652 ns/op 2 B/op 2 allocs/op
BenchmarkMarshalXMLStd10-4 200000 7533 ns/op 11 B/op 11 allocs/op
BenchmarkMarshalXMLStd100-4 20000 65763 ns/op 195 B/op 101 allocs/op
BenchmarkMarshalXMLStd1000-4 2000 663373 ns/op 3522 B/op 1002 allocs/op
BenchmarkMarshalXMLQuickTemplate1-4 10000000 145 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalXMLQuickTemplate10-4 3000000 597 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalXMLQuickTemplate100-4 300000 5833 ns/op 0 B/op 0 allocs/op
BenchmarkMarshalXMLQuickTemplate1000-4 30000 53000 ns/op 32 B/op 0 allocs/op
-
Why is the quicktemplate syntax incompatible with html/template?
Because
html/templatesyntax isn't expressive enough forquicktemplate. -
What's the difference between quicktemplate and ego?
Egois similar toquicktemplatein the sense it converts templates into Go code. But it misses the following stuff, which makesquicktemplateso 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 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?
Gorazoris similar toquicktemplatein the sense it converts templates into Go code. But it misses the following useful features:- Clear syntax instead of hard-to-understand magic stuff related to template arguments, template inheritance and embedding function templates into other templates.
-
Is there a syntax highlighting for qtpl files?
Yes - see this issue for details. If you are using JetBrains products (syntax highlighting and autocomplete):
- cd JetBrains settings directory
- mkdir -p filetypes && cd filetypes
- curl https://raw.githubusercontent.com/valyala/quicktemplate/master/QuickTemplate.xml >> QuickTemplate.xml
- Restart your IDE
-
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