As I have been rewriting my cryptocurrency with PHP for Go for 8 months. Part 2

The 2nd part of the story, which began with a text message from Kati "Do not call and do not write me more !!!!"

The first part is here . For those who are too lazy to read, I will give a summary:

4.5 years ago I had the imprudence to start writing my cryptocurrency in a completely inappropriate language for this business - in PHP. As a result, of course, I wrote (I am stubborn), but it turned out to be a crutch on a crutch and that it worked at all was just some kind of magic.
I just want to warn you, I’m a self-taught programmer and I write code, to say the least, imperfectly.
')
It all started with the fact that I broke up with a girl named Katya and on the same day (April 4, 2015) decided to study Go and rewrite my cryptocurrency. For those who are interested in what's up with Katya, I made spoilers, but who are not interested, just do not pay attention to Katya


A total of 8 months: the application runs on Win ( 64/32 ), OSX (64/32), Linux (64/32), FreeBSD (64/32), Android , IOS (it will be cool if someone throws on the App Store ).
General code ~ 73k lines, code for different OS somewhere a few hundred lines.
40k - processing / generation of blocks / tr-y, 17.5k - controllers for the interface, 15.5k - templates
PostgreSQL, SQLite, MySQL are supported.

Those who will test my creation, I warn you - there may be bugs, and if you have time, write about them, please, at darwin@dcoin.club or in a personal on Habré. Suggestions and advice are also welcome.

In the first part, I talked about how a web server operates in dcoin.

In this article I will describe how I use the html / template

Templates

To generate HTML pages in Go there is a very convenient package - html / template. The easiest way to understand how it works is to experiment with this example . As a rule, the templates are stored in separate html files, but in the examples on play.golang.org, for clarity, the templates are inserted into the go-code.

Most of the information on the templates I received from gohugo.io/templates/go-templates

My templates are here . Each template begins with the definition of its name {{define "templateName"}}, and ends with {{end}}

Controllers that use templates get html code through the function makeTemplate . In it, I pass the name of the html file, the name of the template (which is specified in {{define}}), parameters.

TemplateStr, err := makeTemplate("template_name", "templateName", &tplPage{ Alert: c.Alert, Lang: c.Lang, TxType: txType, TxTypeId: txTypeId}) 

The set of bytes received in TemplateStr is transferred to content.go and as a result, the browser gets the generated html-page

In the makeTemplate for all templates, I include additional templates, such as signatures.html, alert_success.html. And also, add custom functions (FuncMap), which are used to process data in templates.

Inclusions in templates

To include another template in the template you need to use the {{{template "signatures" construct }}. The dot at the end says that you need to process all the parameters in the signatures template; without a dot, the parameters will not be processed. I add signatures to almost all templates, here’s an example

Options

Comparison I will cite several examples at once to show how simple it is:

 {{if not .UserID}} <span></span> {{end}} {{if .UserID}} <span> </span> {{end}} {{if eq .UserID 0}} <span>UserID == 0</span> {{end}} {{if ne .UserID 0}} <span>UserID != 0</span> {{end}} {{if lt .UserID 0}} <span>UserID < 0</span> {{end}} {{if le .UserID 0}} <span>UserID <= 0</span> {{end}} {{if gt .UserID 0}} <span>UserID > 0</span> {{end}} {{if ge .UserID 0}} <span>UserID >= 0</span> {{end}} 

{{.Lang.pool} - Lang is a map. Those. through the point we get the value, which has the key “pool”

User Functions

The html-code in the variables needs to be disassembled. To do this, add a function:

 funcMap := template.FuncMap{ "noescape": func(s string) template.HTML { return template.HTML(s) }, } 

All user functions are collected in my makeTemplate . Use this:

 {{noescape .Lang.htmlText}} 

Range

To disassemble any map used Range. Here is an example taken from here :

 {{range $k, $country := .Countries}} <option value='{{$k}}' {{if eq $k $.MyCountry}} selected {{end}}>{{$country}}</option> {{end}} 

From the code, probably, it is clear what is happening. But I want to pay special attention to $ .MyCountry. If you do not add $, then access to the .MyCountry parameter will not be. At first, I often forgot about it and thought for a long time what was wrong. Outside of range, access to MyCountry is again obtained through {{.MyCountry}}

Variables

In templates, you can create your own variables. Here is an example taken from here :

 {{range $i, $pageType := .PagesArray}} {{$counter := ""}} {{if eq $pageType "funders"}} {{$counter := " <span class='count h6 bg-grey-dark white'>{{$.ProjectCountFunders}}</span>"}} {{else if eq $pageType "comments"}} {{$counter := " <span class='count h6 bg-grey-dark white'>{{$.ProjectCountComments}}</span>"}} {{end}} {{$counter}} {{end}} 

In this example, a new $ counter variable is created, which is assigned a value, depending on the condition, and its result is displayed below.

and / or

The logic of work and / or turned out to be somewhat unusual for me.
Examples:

 {{if and (eq .Start 1) (ne .BlockId 1) (gt .UserId 0)}} 

If .Start == 1 and .BlockId! = 1 and .UserId> 0

 {{if or (eq .Start 1) (ne .BlockId 1) (gt .UserId 0)}} 

If .Start == 1 or .BlockId! = 1 or .UserId> 0

Js code

Another problem took me quite a lot of time. If you need to generate some js-code in the controller, for example:

 var x="1"; 

Then, when outputting it in the template via {{.SomeJSCode}} we get

 "var x=\"1\";" 

Solution 1

noescape will not help here. You need to add a new custom function:

 "js": func(s string) template.JS { return template.JS(s) }, 

And in the template use {{js .SomeJSCode}}

Solution 2

In the controller, use the template.JS type. Before converting the variable string: template.JS (SomeJsStringVariable). In the template itself, in this case you need to output {{.SomeJSCode}}

Conclusion

In the following articles, I will talk about the database, smooth application termination via signals, blockchain block processing, GO encryption and JS decryption, how I changed gomobile a little, adding notifications and background work for IOS and Android applications.