Why does this codeblock execute after Rails.cache.fetch
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I have this line of code which performs exactly what I want it to do. But I have no idea why it works.
Rails.cache.fetch(key, expires_in: 1.day) do
a << b
end
What it is supposed to do is add b to a if the key does not exist in the Rails cache.
Why i'm confused?
Rails.cache.fetch(key, expires_in: 1.day)
returns nil, regardless if the key was already in the cache.
question:
why does the code block run when there is no key in the cache, but doesn't run otherwise?
Extra details: Rails cache is connected to Redis.
ruby-on-rails ruby redis codeblocks
asked Nov 16 '18 at 14:37
MakotoMakoto
51
add a comment |
I have this line of code which performs exactly what I want it to do. But I have no idea why it works.
Rails.cache.fetch(key, expires_in: 1.day) do
a << b
end
What it is supposed to do is add b to a if the key does not exist in the Rails cache.
Why i'm confused?
Rails.cache.fetch(key, expires_in: 1.day)
returns nil, regardless if the key was already in the cache.
question:
why does the code block run when there is no key in the cache, but doesn't run otherwise?
Extra details: Rails cache is connected to Redis.
ruby-on-rails ruby redis codeblocks
asked Nov 16 '18 at 14:37
MakotoMakoto
51
add a comment |
I have this line of code which performs exactly what I want it to do. But I have no idea why it works.
Rails.cache.fetch(key, expires_in: 1.day) do
a << b
end
What it is supposed to do is add b to a if the key does not exist in the Rails cache.
Why i'm confused?
Rails.cache.fetch(key, expires_in: 1.day)
returns nil, regardless if the key was already in the cache.
question:
why does the code block run when there is no key in the cache, but doesn't run otherwise?
Extra details: Rails cache is connected to Redis.
ruby-on-rails ruby redis codeblocks
asked Nov 16 '18 at 14:37
MakotoMakoto
51
I have this line of code which performs exactly what I want it to do. But I have no idea why it works.
Rails.cache.fetch(key, expires_in: 1.day) do
a << b
end
What it is supposed to do is add b to a if the key does not exist in the Rails cache.
Why i'm confused?
Rails.cache.fetch(key, expires_in: 1.day)
returns nil, regardless if the key was already in the cache.
question:
why does the code block run when there is no key in the cache, but doesn't run otherwise?
Extra details: Rails cache is connected to Redis.
ruby-on-rails ruby redis codeblocks
ruby-on-rails ruby redis codeblocks
asked Nov 16 '18 at 14:37
MakotoMakoto
51
asked Nov 16 '18 at 14:37
MakotoMakoto
51
asked Nov 16 '18 at 14:37
MakotoMakoto
51
asked Nov 16 '18 at 14:37
MakotoMakoto
51
asked Nov 16 '18 at 14:37
MakotoMakoto
51
51
add a comment |
add a comment |
1 Answer
1
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oldest
votes
It might be confusing that the do ... end block is evaluated although Rails.cache.fetch returns nil. But the do ... end block doesn't run on top of the nil response.
In fact, the do ... end block is an additional argument to the fetch method call. Have a look at the source code of fetch.
Without a block fetch basically does only one thing – calling read(name, options) in line 328. But with a block it way more (lines 307 to 324)
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
fabulous thanks. This also led me to a solution to my spec problems. 'allow(Rails.cache).to receive(:fetch).and_yield' solved them
– Makoto
Nov 16 '18 at 14:56
add a comment |
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1 Answer
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1 Answer
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active
oldest
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active
oldest
votes
It might be confusing that the do ... end block is evaluated although Rails.cache.fetch returns nil. But the do ... end block doesn't run on top of the nil response.
In fact, the do ... end block is an additional argument to the fetch method call. Have a look at the source code of fetch.
Without a block fetch basically does only one thing – calling read(name, options) in line 328. But with a block it way more (lines 307 to 324)
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
fabulous thanks. This also led me to a solution to my spec problems. 'allow(Rails.cache).to receive(:fetch).and_yield' solved them
– Makoto
Nov 16 '18 at 14:56
add a comment |
It might be confusing that the do ... end block is evaluated although Rails.cache.fetch returns nil. But the do ... end block doesn't run on top of the nil response.
In fact, the do ... end block is an additional argument to the fetch method call. Have a look at the source code of fetch.
Without a block fetch basically does only one thing – calling read(name, options) in line 328. But with a block it way more (lines 307 to 324)
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
fabulous thanks. This also led me to a solution to my spec problems. 'allow(Rails.cache).to receive(:fetch).and_yield' solved them
– Makoto
Nov 16 '18 at 14:56
add a comment |
It might be confusing that the do ... end block is evaluated although Rails.cache.fetch returns nil. But the do ... end block doesn't run on top of the nil response.
In fact, the do ... end block is an additional argument to the fetch method call. Have a look at the source code of fetch.
Without a block fetch basically does only one thing – calling read(name, options) in line 328. But with a block it way more (lines 307 to 324)
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
It might be confusing that the do ... end block is evaluated although Rails.cache.fetch returns nil. But the do ... end block doesn't run on top of the nil response.
In fact, the do ... end block is an additional argument to the fetch method call. Have a look at the source code of fetch.
Without a block fetch basically does only one thing – calling read(name, options) in line 328. But with a block it way more (lines 307 to 324)
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
answered Nov 16 '18 at 14:50
spickermannspickermann
61.5k75881
61.5k75881
fabulous thanks. This also led me to a solution to my spec problems. 'allow(Rails.cache).to receive(:fetch).and_yield' solved them
– Makoto
Nov 16 '18 at 14:56
add a comment |
fabulous thanks. This also led me to a solution to my spec problems. 'allow(Rails.cache).to receive(:fetch).and_yield' solved them
– Makoto
Nov 16 '18 at 14:56
fabulous thanks. This also led me to a solution to my spec problems. 'allow(Rails.cache).to receive(:fetch).and_yield' solved them
– Makoto
Nov 16 '18 at 14:56
fabulous thanks. This also led me to a solution to my spec problems. 'allow(Rails.cache).to receive(:fetch).and_yield' solved them
– Makoto
Nov 16 '18 at 14:56
add a comment |
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