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change to write! macro

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Dhghomon 2020-08-21 15:27:14 +09:00 committed by GitHub
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@ -12316,8 +12316,7 @@ Error: Os { code: 80, kind: AlreadyExists, message: "The file exists." }
Let's try using `.append()` so we can write to a file. To write to the file we can use `.write_all()`, which is a method that tries to write in everything you give it. Let's try using `.append()` so we can write to a file. To write to the file we can use `.write_all()`, which is a method that tries to write in everything you give it.
Also, let's try out another macro called `include_str!`. This macro will just try to make a file into a `&str` without having to do anything else - all you have to do is give it the file name. Also, we will use the `write!` macro to do the same thing. You will remember this macro from when we did `impl Display` for our structs. This time we are using it on a file though instead of a buffer.
```rust ```rust
use std::fs; use std::fs;
@ -12333,10 +12332,13 @@ Dad: Yep. The world didn't turn color until sometimes in the 1930s...")?;
let mut calvin_file = OpenOptions::new() let mut calvin_file = OpenOptions::new()
.append(true) // Now we can write without deleting it .append(true) // Now we can write without deleting it
.read(true)
.open("calvin_with_dad.txt")?; .open("calvin_with_dad.txt")?;
calvin_file.write_all(b"And it was a pretty grainy color for a while too.")?; calvin_file.write_all(b"And it was a pretty grainy color for a while too.\n")?;
write!(&mut calvin_file, "That's really weird.\n")?;
write!(&mut calvin_file, "Well, truth is stranger than fiction.")?;
println!("{}", include_str!("calvin_with_dad.txt")); println!("{}", fs::read_to_string("calvin_with_dad.txt")?);
Ok(()) Ok(())
} }
@ -12349,4 +12351,6 @@ Calvin: Dad, how come old photographs are always black and white? Didn't they ha
Dad: Sure they did. In fact, those photographs *are* in color. It's just the *world* was black and white then. Dad: Sure they did. In fact, those photographs *are* in color. It's just the *world* was black and white then.
Calvin: Really? Calvin: Really?
Dad: Yep. The world didn't turn color until sometimes in the 1930s...And it was a pretty grainy color for a while too. Dad: Yep. The world didn't turn color until sometimes in the 1930s...And it was a pretty grainy color for a while too.
That's really weird.
Well, truth is stranger than fiction.
``` ```