Introduction In episode 8, Miki developed a Go HTTP client that had a method to check the health of a theoretical API. The method would construct the request URL and return an error based on the response code received from the server. Miki then created a type that would mock Go’s http.RoundTripper interface and replace his client’s transport with said type to test it. To improve the efficacy, Miki’s stub will simulate an erroneous response to see if his client’s Health method is working as intended.
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Introduction In episode 7, Miki discussed design considerations to keep in mind while creating interfaces in Go with the first idea he proposed being that an interface should represent what we need from a type, and not what is stored on the type. To add some clarity to this thought, Miki explained how the io.Reader and io.Writer interfaces each require one method to be implemented although the underlying concrete type may store more information.
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Introduction In episode 6, Miki built a logger package with the aim of making it as versatile as possible. To achieve this, he constructed his logger object with a function that would: accept the io.Writer interface as a parameter and perform type assertions to retrieve other interface types as needed. By building this, Miki demonstrated how polymorphism is achieved with Go by changing the type of a variable with type assertions.
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Introduction One of the exercises I give to students is to download a single big file over HTTP concurrently using several goroutines using HTTP Range requests. An extra part of the exercise is to validate the downloaded file from a known MD5 signature. This extra part turns out to be interesting, let’s have a look. Getting Download Information Let’s make an HTTP HEAD request to get information about a file located in a public dataset stored on Google Cloud Storage (GCS).
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with Cheikh Seck Introduction This is the first in a series of posts that will explore the Rust programming language. I am going to take the same approach I did with Go and write little programs that explore the different features of the language. Before I begin that work, I thought it would be fun to write a program that does something fun. In this post and my first ever Rust program, I’m going to use a Rust library called bracket-lib that provides a cross-platform terminal emulator.
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Introduction In episode 5, Miki wrote a function that counted the number of lines in a file with interfaces. The first thing his function did was to open a file with Go’s os.Open function. Miki chose this method because the variable returned by said function implements the io.Reader interface which is crucial for the next step. The remaining parts of this function consisted of a primitive type alias that satisfied the io.
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Introduction In episode 4, Miki defined an enumerated type that satisfied Go’s fmt.Stringer interface. By implementing the fmt.Stringer interface, Miki can specify how his enumerators were printed within a formatted string and in this case, he expected the values to be displayed as a predetermined text value. Miki also pointed out how using the value of the method’s receiver within the Stringer method can result in a recursive loop.
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Introduction In episode 3, Miki implemented a type that satisfied Go’s error interface. The odd thing about his type was it would be considered not-nil although no value was set for it. To get a better understanding of the situation, Miki gives a brief explanation of how Go determines if an error value is nil, and in this case, Miki specified the type of the variable returned to be a pointer of his custom error type which blindsided Go’s mechanism to determine a nil value.
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Introduction In episode 2, Miki examined the impact interfaces have on the performance of a Go program. To perform this experiment, Miki invoked a type’s method in two ways: with the concrete type and as an interface function to measure the difference in execution time. The conclusion of this experiment was that calling a method with the concrete type is faster than using an interface. During the experiment, Miki made use of the build flag -gcflag=’-m’ to display which variables were being allocated on the heap and where the compiler was automatically inlining function calls.
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Introduction In episode 1, Miki had two functions that performed the similar operation, but returned different types. To refactor this, Miki rewrote both functions as a generic function that allowed him to specify the type to be returned during invocation. In some cases, the compiler may not recognise a type, thus, Miki gives a few pointers on manually telling a generic function which type to use. After demonstrating how to return different types with a generic function, Miki limited the types his generic function would accept with an interface.
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