其他
鹅厂练习13年Coding后，我悟了
👉导读
本文主要受《程序员修炼之道: 通向务实的最高境界》、《架构整洁之道》、《Unix 编程艺术》启发。我不是第一个发明这些原则的人，甚至不是第一个总结出来的人，别人都已经写成书了！务实的程序员对于方法的总结，总是殊途同归。👉目录
1 细节即是架构2 把代码和文档绑在一起3 ETC 价值观4 DRY 原则……19 SOLID20 一个函数不要出现多个层级的代码21 Unix 哲学基础01
一直以来，设计(Design)和架构(Architecture)这两个概念让大多数人十分迷惑--什么是设计？什么是架构？二者究竟有什么区别？二者没有区别。一丁点区别都没有！"架构"这个词往往适用于"高层级"的讨论中，这类讨论一般都把"底层"的实现细节排除在外。而"设计"一词，往往用来指代具体的系统底层组织结构和实现的细节。但是，从一个真正的系统架构师的日常工作来看，这些区分是根本不成立的。以给我设计新房子的建筑设计师要做的事情为例。新房子当然是存在着既定架构的，但这个架构具体包含哪些内容呢？首先，它应该包括房屋的形状、外观设计、垂直高度、房间的布局，等等。
但是，如果查看建筑设计师使用的图纸，会发现其中也充斥着大量的设计细节。譬如，我们可以看到每个插座、开关以及每个电灯具体的安装位置，同时也可以看到某个开关与所控制的电灯的具体连接信息；我们也能看到壁炉的具体位置，热水器的大小和位置信息，甚至是污水泵的位置；同时也可以看到关于墙体、屋顶和地基所有非常详细的建造说明。总的来说，架构图里实际上包含了所有的底层设计细节，这些细节信息共同支撑了顶层的架构设计，底层设计信息和顶层架构设计共同组成了整个房屋的架构文档。
软件设计也是如此。底层设计细节和高层架构信息是不可分割的。他们组合在一起，共同定义了整个软件系统，缺一不可。所谓的底层和高层本身就是一系列决策组成的连续体，并没有清晰的分界线。
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ETC 是一种价值观念，不是一条原则。价值观念是帮助你做决定的: 我应该做这个，还是做那个？当你在软件领域思考时，ETC 是个向导，它能帮助你在不同的路线中选出一条。就像其他一些价值观念一样，你应该让它漂浮在意识思维之下，让它微妙地将你推向正确的方向。
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package dippackage diptype Botton interface { TurnOn() TurnOff()}type UI struct { botton Botton}func NewUI(b Botton) *UI { return &UI{botton: b}}func (u *UI) Poll() { u.botton.TurnOn() u.botton.TurnOff() u.botton.TurnOn()}package javaimplimport "fmt"type Lamp struct {}func NewLamp() *Lamp { return &Lamp{}}func (*Lamp) TurnOn() { fmt.Println("turn on java lamp")}func (*Lamp) TurnOff() { fmt.Println("turn off java lamp")}package pythonimplimport "fmt"type Lamp struct {}func NewLamp() *Lamp { return &Lamp{}}func (*Lamp) TurnOn() { fmt.Println("turn on python lamp")}func (*Lamp) TurnOff() { fmt.Println("turn off python lamp")}package mainimport ( "javaimpl" "pythonimpl" "dip")func runPoll(b dip.Botton) { ui := NewUI(b) ui.Poll()}func main() { runPoll(pythonimpl.NewLamp()) runPoll(javaimpl.NewLamp())}09
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func applyDiscount(customer Customer, orderID string, discount float32) { customer. Orders. Find(orderID). GetTotals(). ApplyDiscount(discount)}func applyDiscount(customer Customer, orderID string, discount float32) { customer. FindOrder(orderID). GetTotals(). ApplyDiscount(discount)}func applyDiscount(customer Customer, orderID string, discount float32) { customer. FindOrder(orderID). ApplyDiscount(discount)}func applyDiscount(customer Customer, orderID string, discount float32) { total := customer. FindOrder(orderID). GetTotals() customer. FindOrder(orderID). SetTotal(total*discount)}14
func amount(customer Customer) float32 { return customer.Orders.Last().Totals().Amount}func amount(totals Totals) float32 { return totals.Amount}15
继承就是耦合。不仅子类耦合到父类，以及父类的父类等，而且使用子类的代码也耦合到所有祖先类。有些人认为继承是定义新类型的一种方式。他们喜欢设计图表，会展示出类的层次结构。他们看待问题的方式，与维多利亚时代的绅士科学家们看待自然的方式是一样的，即将自然视为须分解到不同类别的综合体。不幸的是，这些图表很快就会为了表示类之间的细微差别而逐层添加，最终可怕地爬满墙壁。由此增加的复杂性，可能使应用程序更加脆弱，因为变更可能在许多层次之间上下波动。因为一些值得商榷的词义消歧方面的原因，C++在20世纪90年代玷污了多重继承的名声。结果许多当下的 OO 语言都没有提供这种功能。
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Exceptions are preferred in modern C++ for the following reasons:
* An exception forces calling code to recognize an error condition and handle it. Unhandled exceptions stop program execution.* An exception jumps to the point in the call stack that can handle the error. Intermediate functions can let the exception propagate. They don't have to coordinate with other layers.* The exception stack-unwinding mechanism destroys all objects in scope after an exception is thrown, according to well-defined rules.* An exception enables a clean separation between the code that detects the error and the code that handles the error.Because most existing C++ code at Google is not prepared to deal with exceptions, it is comparatively difficult to adopt new code that generates exceptions.19
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// IrisFriends 拉取好友func IrisFriends(ctx iris.Context, app *app.App) { var rsp sdc.FriendsRsp defer func() { var buf bytes.Buffer _ = (&jsonpb.Marshaler{EmitDefaults: true}).Marshal(&buf, &rsp) _, _ = ctx.Write(buf.Bytes()) }() common.AdjustCookie(ctx) if !checkCookie(ctx) { return } // 从cookie中拿到关键的登陆态等有效信息 var session common.BaseSession common.GetBaseSessionFromCookie(ctx, &session) // 校验登陆态 err := common.CheckLoginSig(session, app.ConfigStore.Get().OIDBCmdSetting.PTLogin) if err != nil { _ = common.ErrorResponse(ctx, errors.PTSigErr, 0, "check login sig error") return } if err = getRelationship(ctx, app.ConfigStore.Get().OIDBCmdSetting, NewAPI(), &rsp); err != nil { // TODO:日志 } return}21
Keep It Simple Stupid!
原则3 组合原则: 设计时考虑拼接组合
关于 OOP，关于继承，我前面已经说过了。那我们怎么组织自己的模块？对，用组合的方式来达到。linux 操作系统离我们这么近，它是怎么架构起来的？往小里说，我们一个串联一个业务请求的数据集合，如果使用 BaseSession，XXXSession inherit BaseSession 的设计，其实，这个继承树，很难适应层出不穷的变化。但是如果使用组合，就可以拆解出 UserSignature 等等各种可能需要的部件，在需要的时候组合使用，不断添加新的部件而没有对老的继承树的记忆这个心智负担。
// A Request represents an HTTP request received by a server// or to be sent by a client.//// The field semantics differ slightly between client and server// usage. In addition to the notes on the fields below, see the// documentation for Request.Write and RoundTripper.type Request struct { // Method specifies the HTTP method (GET, POST, PUT, etc.). // For client requests, an empty string means GET. // // Go's HTTP client does not support sending a request with // the CONNECT method. See the documentation on Transport for // details. Method string
// URL specifies either the URI being requested (for server // requests) or the URL to access (for client requests). // // For server requests, the URL is parsed from the URI // supplied on the Request-Line as stored in RequestURI. For // most requests, fields other than Path and RawQuery will be // empty. (See RFC 7230, Section 5.3) // // For client requests, the URL's Host specifies the server to // connect to, while the Request's Host field optionally // specifies the Host header value to send in the HTTP // request. URL *url.URL
// The protocol version for incoming server requests. // // For client requests, these fields are ignored. The HTTP // client code always uses either HTTP/1.1 or HTTP/2. // See the docs on Transport for details. Proto string // "HTTP/1.0" ProtoMajor int // 1 ProtoMinor int // 0
// Header contains the request header fields either received // by the server or to be sent by the client. // // If a server received a request with header lines, // // Host: example.com // accept-encoding: gzip, deflate // Accept-Language: en-us // fOO: Bar // foo: two // // then // // Header = map[string][]string{ // "Accept-Encoding": {"gzip, deflate"}, // "Accept-Language": {"en-us"}, // "Foo": {"Bar", "two"}, // } // // For incoming requests, the Host header is promoted to the // Request.Host field and removed from the Header map. // // HTTP defines that header names are case-insensitive. The // request parser implements this by using CanonicalHeaderKey, // making the first character and any characters following a // hyphen uppercase and the rest lowercase. // // For client requests, certain headers such as Content-Length // and Connection are automatically written when needed and // values in Header may be ignored. See the documentation // for the Request.Write method. Header Header
// Body is the request's body. // // For client requests, a nil body means the request has no // body, such as a GET request. The HTTP Client's Transport // is responsible for calling the Close method. // // For server requests, the Request Body is always non-nil // but will return EOF immediately when no body is present. // The Server will close the request body. The ServeHTTP // Handler does not need to. Body io.ReadCloser
// GetBody defines an optional func to return a new copy of // Body. It is used for client requests when a redirect requires // reading the body more than once. Use of GetBody still // requires setting Body. // // For server requests, it is unused. GetBody func() (io.ReadCloser, error)
// ContentLength records the length of the associated content. // The value -1 indicates that the length is unknown. // Values >= 0 indicate that the given number of bytes may // be read from Body. // // For client requests, a value of 0 with a non-nil Body is // also treated as unknown. ContentLength int64
// TransferEncoding lists the transfer encodings from outermost to // innermost. An empty list denotes the "identity" encoding. // TransferEncoding can usually be ignored; chunked encoding is // automatically added and removed as necessary when sending and // receiving requests. TransferEncoding []string
// Close indicates whether to close the connection after // replying to this request (for servers) or after sending this // request and reading its response (for clients). // // For server requests, the HTTP server handles this automatically // and this field is not needed by Handlers. // // For client requests, setting this field prevents re-use of // TCP connections between requests to the same hosts, as if // Transport.DisableKeepAlives were set. Close bool
// For server requests, Host specifies the host on which the // URL is sought. For HTTP/1 (per RFC 7230, section 5.4), this // is either the value of the "Host" header or the host name // given in the URL itself. For HTTP/2, it is the value of the // ":authority" pseudo-header field. // It may be of the form "host:port". For international domain // names, Host may be in Punycode or Unicode form. Use // golang.org/x/net/idna to convert it to either format if // needed. // To prevent DNS rebinding attacks, server Handlers should // validate that the Host header has a value for which the // Handler considers itself authoritative. The included // ServeMux supports patterns registered to particular host // names and thus protects its registered Handlers. // // For client requests, Host optionally overrides the Host // header to send. If empty, the Request.Write method uses // the value of URL.Host. Host may contain an international // domain name. Host string
// Form contains the parsed form data, including both the URL // field's query parameters and the PATCH, POST, or PUT form data. // This field is only available after ParseForm is called. // The HTTP client ignores Form and uses Body instead. Form url.Values
// PostForm contains the parsed form data from PATCH, POST // or PUT body parameters. // // This field is only available after ParseForm is called. // The HTTP client ignores PostForm and uses Body instead. PostForm url.Values
// MultipartForm is the parsed multipart form, including file uploads. // This field is only available after ParseMultipartForm is called. // The HTTP client ignores MultipartForm and uses Body instead. MultipartForm *multipart.Form
// Trailer specifies additional headers that are sent after the request // body. // // For server requests, the Trailer map initially contains only the // trailer keys, with nil values. (The client declares which trailers it // will later send.) While the handler is reading from Body, it must // not reference Trailer. After reading from Body returns EOF, Trailer // can be read again and will contain non-nil values, if they were sent // by the client. // // For client requests, Trailer must be initialized to a map containing // the trailer keys to later send. The values may be nil or their final // values. The ContentLength must be 0 or -1, to send a chunked request. // After the HTTP request is sent the map values can be updated while // the request body is read. Once the body returns EOF, the caller must // not mutate Trailer. // // Few HTTP clients, servers, or proxies support HTTP trailers. Trailer Header
// RemoteAddr allows HTTP servers and other software to record // the network address that sent the request, usually for // logging. This field is not filled in by ReadRequest and // has no defined format. The HTTP server in this package // sets RemoteAddr to an "IP:port" address before invoking a // handler. // This field is ignored by the HTTP client. RemoteAddr string
// RequestURI is the unmodified request-target of the // Request-Line (RFC 7230, Section 3.1.1) as sent by the client // to a server. Usually the URL field should be used instead. // It is an error to set this field in an HTTP client request. RequestURI string
// TLS allows HTTP servers and other software to record // information about the TLS connection on which the request // was received. This field is not filled in by ReadRequest. // The HTTP server in this package sets the field for // TLS-enabled connections before invoking a handler; // otherwise it leaves the field nil. // This field is ignored by the HTTP client. TLS *tls.ConnectionState
// Cancel is an optional channel whose closure indicates that the client // request should be regarded as canceled. Not all implementations of // RoundTripper may support Cancel. // // For server requests, this field is not applicable. // // Deprecated: Set the Request's context with NewRequestWithContext // instead. If a Request's Cancel field and context are both // set, it is undefined whether Cancel is respected. Cancel <-chan struct{}
// Response is the redirect response which caused this request // to be created. This field is only populated during client // redirects. Response *Response
// ctx is either the client or server context. It should only // be modified via copying the whole Request using WithContext. // It is unexported to prevent people from using Context wrong // and mutating the contexts held by callers of the same request. ctx context.Context}原则 6 吝啬原则: 除非确无它法, 不要编写庞大的程序
原则 7 透明性原则: 设计要可见，以便审查和调试
原则 10 通俗原则: 接口设计避免标新立异
type Point struct { X float64 Y float64}type Point struct { VerticalOrdinate float64 HorizontalOrdinate float64}原则 11 缄默原则: 如果一个程序没什么好说的，就沉默
原则 12 补救原则: 出现异常时，马上退出并给出足够错误信息
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